Just Use Any: js.la Edition

TypeScript has won the hearts and minds of programmers all around the world. Unfortunately, your deadlines are due yesterday, your boss is unconvinced, and your team remains skeptical. What's a TypeScript enthusiast to do? Join me on a journey of self-discovery: we'll learn what it means to lead by influence and level up our effectiveness as engineers. Then, an exploration of the value to engineering and business brought about by type systems (with some math to prove it). To tie it all together, we'll explore this through the lens of real world stories from Netflix, where we use TypeScript to modernize filmmaking.

Transcript

1. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   Just Use Any
   Lauren Tan (she/her)
   PRESENTED BY
   unknown
   

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2. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   type Spiderman
   SKIP INTRO
   

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3. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   Type systems at
   ${work}.
   

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4. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   https://jobs.netflix.com/
   

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5. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   Type Systems at
   Netflix
   Studio UI.
   We're hiring UI Engineers in LA!
   

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6. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   Studio UI
   Foundations.
   react
   redux*
   Apollo GraphQL
   TypeScript
   gatsby/Next.js
   lerna
   yarn
   ???
   Top secret stuff
   Designed by Sophinie Som
   https://jobs.netflix.com/jobs/870589 (my awesome team)
   

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7. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   TypeScript.
   GraphQL.
   gRPC.
   JVM.
   

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8. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   Making the case for
   typed JavaScript at
   Netflix.
   

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9. ! sugarpirate_ " poteto
   Just Use Any
   js.la 2020, Los Angeles, CA
   1. Improve developer
   productivity.
   Making the case for typed JavaScript at Netflix.
   

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10. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    2. Reduce bugs.
    Making the case for typed JavaScript at Netflix.
    

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11. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    3. Performance*.
    Making the case for typed JavaScript at Netflix.
    

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12. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    https://mrale.ph/blog/2015/01/11/whats-up-with-monomorphism.html
    

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13. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    4. End to end type safety.
    Making the case for typed JavaScript at Netflix.
    

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14. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    We also considered the
    risks of adopting typed
    JavaScript.
    Making the case for typed JavaScript at Netflix.
    

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15. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    TypeScript checked most
    of those boxes.
    Making the case for typed JavaScript at Netflix.
    

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16. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Building a community.
    

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17. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    

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18. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    MY CODEBASE
    AFTER 3.7 LANDS
    yay!?.optional!?.chaining
    

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19. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    

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20. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    • Matt Greer - Type Widening
    • Ryan Anklam - TVUI's
    Experience with TypeScript
    Tim Branyen - Experience
    Using TypeScript in AppDirectory
    • Jordan Gensler - How To Type
    Everything
    • Danny Cochran - TypeScript with
    Maple
    • Randy Wenas - TS at Employee
    Apps
    • Emily Dobervich - TypeScript is
    just JavaScript
    • Young Min Kim -
    Using TypeScript Today
    Passionate
    TypeScript
    users at
    Netflix.
    Building a community.
    

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21. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    "Prefer statically typed [!!...] for better
    developer productivity"
    

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22. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    TypeScript.
    GraphQL.
    gRPC.
    JVM.
    

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23. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    bit.ly/swipe-left
    

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24. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Djikstra, supposedly
    "If debugging is the process of
    removing software bugs, then
    programming must be the process
    of putting them in."
    

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25. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    
    

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26. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    "A type system is a tractable
    syntactic method for proving the
    absence of certain program
    behaviors by classifying phrases
    according to the kinds of values
    they compute."
    Types and Programming Languages, Benjamin C. Pierce
    

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27. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    

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28. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    How many ways can this
    program fail?
    

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29. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    const half = x !=> x / 2;
    

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30. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    const TEST_CASES = [
    null,
    undefined,
    Symbol(1),
    10,
    '10',
    'hello world',
    { name: 'Lauren' },
    [1, 2, 3],
    x !=> x * x
    ];
    

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31. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    TEST_CASES.map(testValue !=> {
    return {
    result: half(testValue),
    test: testValue.toString()
    }
    });
    

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32. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    not my type!
    

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33. ! sugarpirate_ " poteto
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    js.la 2020, Los Angeles, CA
    TEST_CASES.map(testValue !=> {
    return {
    result: half(testValue),
    test: testValue.toString()
    } ^^^^^^^^^^
    });
    

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34. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    

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35. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Spend less time
    debugging, and more
    time writing code.
    

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36. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    

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37. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    

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38. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    const TEST_CASES = [
    null, !// Uncaught TypeError
    undefined, !// Uncaught TypeError
    Symbol(1), !// Uncaught TypeError
    10, !// 5
    '10', !// 5
    'hello world', !// NaN
    { name: 'Lauren' }, !// NaN
    [1, 2, 3], !// NaN
    x !=> x * x !// NaN
    ];
    

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39. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    How many ways can this
    program fail? (Infinity)
    

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40. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    const half = (x: number) !=> x / 2;
    

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41. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    How many ways can this
    program fail (at compile
    time)?
    

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42. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    0*.
    

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43. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Less is better.
    

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44. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    What are types
    anyway?
    

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45. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    A type is the set of
    possible values for
    a term.
    

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46. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    string
    type T1 = string
    '中⽂'
    'español'
    '⽇本語'
    'js.la'
    '2019'
    '✌'
    

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47. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    number
    number
    type T2 = number
    2019
    NaN
    Infinity
    123.45
    0x11
    123e-1
    
    

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48. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    type T3 = string | number
    '中⽂'
    'español'
    '⽇本語'
    'js.la'
    '2019'
    '✌'
    2019
    NaN
    Infinity
    123.45
    0x11
    123e-1
    number
    string
    

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49. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Why should I care
    about the cardinality
    of a type?
    cardinality · number of elements of the set
    

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50. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    number
    type T4 = 'TSConf' | 'dotJS' | 'React Rally'
    Cardinality: 3
    'TSConf'
    'dotJS'
    'React Rally'
    

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51. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    number
    type Option = None | Some
    Cardinality: 2
    None
    Some
    https://github.com/gcanti/fp-ts
    

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52. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    number
    Cardinality: Infinity
    undefined
    null
    number
    string
    symbol
    array
    object
    type T5 = unknown
    

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53. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    type T5 = unknown
    *slaps roof of typescript*
    this bad type can fit so many
    types in it
    

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54. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    When we restrict what we can do,
    RUNAR BJARNASON
    it's easier to understand what we
    can do.
    https://youtu.be/GqmsQeSzMdw
    

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55. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Being precise
    helps TypeScript
    help you.
    

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56. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    I had no idea how
    interpreters or
    compilers work. So I
    decided to build one.
    github.com/poteto/boba-js
    

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57. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    !// Integers & arithmetic expressions!!...
    let version = 1 + (50 / 2) - (8 * 3);
    !// !!... and strings
    let name = "The Monkey programming language";
    !// !!... booleans
    let isMonkeyFastNow = true;
    !// !!... arrays & hash maps
    let people = [{"name": "Anna", "age": 24}, {"name": "Bob", "age": 99}];
    monkeylang.org
    

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58. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    !// User-defined functions!!...
    let getName = fn(person) { person["name"]; };
    getName(people[0]); !// !=> "Anna"
    getName(people[1]); !// !=> "Bob"
    !// and built-in functions
    puts(len(people)) !// prints: 2
    

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59. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    let fibonacci = fn(x) {
    if (x !== 0) {
    0
    } else {
    if (x !== 1) {
    return 1;
    } else {
    fibonacci(x - 1) + fibonacci(x - 2);
    }
    }
    };
    

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60. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    !// `newAdder` returns a closure that makes use of the free variables `a` and `b`:
    let newAdder = fn(a, b) {
    fn(c) { a + b + c };
    };
    !// This constructs a new `adder` function:
    let adder = newAdder(1, 2);
    adder(8); !// !=> 11
    

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61. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Lex Parse Evaluate
    Simple interpreter
    architecture.
    

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62. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    V8 architecture.
    

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63. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Lex Parse Evaluate
    Simple interpreter
    architecture.
    

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64. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    let add = fn(x, y) {
    x + y;
    };
    

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65. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    let add = fn(x, y) {
    x + y;
    };
    

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66. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    [
    { type: TokenType.LET, literal: 'let' },
    { type: TokenType.IDENT, literal: 'add' },
    { type: TokenType.ASSIGN, literal: '=' },
    { type: TokenType.FUNCTION, literal: 'fn' },
    { type: TokenType.LPAREN, literal: '(' },
    { type: TokenType.IDENT, literal: 'x' },
    { type: TokenType.COMMA, literal: ',' },
    { type: TokenType.IDENT, literal: 'y' },
    { type: TokenType.RPAREN, literal: ')' },
    { type: TokenType.LBRACE, literal: '{' },
    { type: TokenType.IDENT, literal: 'x' },
    { type: TokenType.PLUS, literal: '+' },
    { type: TokenType.IDENT, literal: 'y' },
    { type: TokenType.SEMICOLON, literal: ';' },
    { type: TokenType.RBRACE, literal: '}' },
    { type: TokenType.SEMICOLON, literal: ';' },
    { type: TokenType.EOF, literal: '' },
    ];
    

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67. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    export type LiteralType = string;
    export type Token = {
    type: TokenType;
    literal: LiteralType;
    };
    

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68. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Lex Parse Evaluate
    Simple interpreter
    architecture.
    

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69. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    [
    LetStatement {
    token: { type: 'LET', literal: 'let' },
    name: Identifier { token: [Object], value: 'add' },
    value: FunctionLiteral {
    token: [Object],
    parameters: [Array],
    body: [BlockStatement]
    }
    }
    ]
    

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70. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    export type BooleanLiteralToken = {
    type: TokenType.TRUE | TokenType.FALSE;
    literal: LiteralType;
    };
    export default class BooleanLiteral implements Expression {
    constructor(public token: BooleanLiteralToken, public value: boolean) {}
    expressionNode() { /** snip **/ }
    tokenLiteral() { /** snip **/ }
    toString() { /** snip **/ }
    }
    

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71. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    export type BooleanLiteralToken = {
    type: TokenType.TRUE | TokenType.FALSE;
    literal: LiteralType;
    };
    export default class BooleanLiteral implements Expression {
    constructor(public token: BooleanLiteralToken, public value: boolean) {}
    expressionNode() { /** snip **/ }
    tokenLiteral() { /** snip **/ }
    toString() { /** snip **/ }
    }
    We only want to create BooleanLiteralASTNodes if we
    encounter a boolean literal Token (true | false)
    

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72. ! sugarpirate_ " poteto
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    js.la 2020, Los Angeles, CA
    !(true !== true);
    

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73. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    !(true !== true);
    currToken
    

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74. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    !(true !== true);
    currToken
    

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75. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    !(true !== true);
    currToken
    

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76. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    export type LiteralType = string;
    export type Token = {
    type: TokenType;
    literal: LiteralType;
    };
    

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77. ! sugarpirate_ " poteto
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    js.la 2020, Los Angeles, CA
    export const enum TokenType {
    ILLEGAL = 'ILLEGAL',
    EOF = 'EOF',
    !// Identifiers + Literals
    IDENT = 'IDENT',
    INT = 'INT',
    !// Operators
    ASSIGN = '=',
    PLUS = '+',
    MINUS = '-',
    BANG = '!',
    ASTERISK = '*',
    SLASH = '/',
    LT = '<',
    GT = '>',
    EQ = '!==',
    NOT_EQ = '!!=',
    !// Delimiters
    COMMA = ',',
    SEMICOLON = ';',
    LPAREN = '(',
    RPAREN = ')',
    LBRACE = '{',
    RBRACE = '}',
    !// Keywords
    FUNCTION = 'FUNCTION',
    LET = 'LET',
    TRUE = 'TRUE',
    FALSE = 'FALSE',
    IF = 'IF',
    ELSE = 'ELSE',
    RETURN = 'RETURN',
    }
    27 types
    of Tokens.
    

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78. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    

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79. ! sugarpirate_ " poteto
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    export default function parseBoolean(this: Parser): Expression {
    return new BooleanLiteral(this.currToken, !/* !!... !*/);
    !// ^^^^^^^^^^^^^^
    !// Argument of type 'Token' is not assignable to parameter of type
    !// 'BooleanLiteralToken'.
    !// Types of property 'type' are incompatible.
    !// Type 'TokenType' is not assignable to type
    !// 'TokenType.TRUE | TokenType.FALSE'.ts(2345)
    }
    this.currToken could be *any* token!
    

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80. ! sugarpirate_ " poteto
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    js.la 2020, Los Angeles, CA
    Type narrowing.
    

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81. ! sugarpirate_ " poteto
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    export default function assertTokenType(
    token: Token,
    !!...assertedTokenTypes: T[]
    ): asserts token is { type: T; literal: LiteralType } {
    const satisfiesAssertion = assertedTokenTypes.some(
    type !=> type !!=== token.type
    );
    if (!satisfiesAssertion) {
    throw new AssertionError({
    message: `Token type is not: ${assertedTokenTypes.join(' OR ')}`,
    });
    }
    }
    

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82. ! sugarpirate_ " poteto
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    js.la 2020, Los Angeles, CA
    export default function assertTokenType(
    token: Token,
    !!...assertedTokenTypes: T[]
    ): asserts token is { type: T; literal: LiteralType } {
    const satisfiesAssertion = assertedTokenTypes.some(
    type !=> type !!=== token.type
    );
    if (!satisfiesAssertion) {
    throw new AssertionError({
    message: `Token type is not: ${assertedTokenTypes.join(' OR ')}`,
    });
    }
    }
    

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83. ! sugarpirate_ " poteto
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    export default function parseBoolean(this: Parser): Expression {
    assertTokenType(this.currToken, TokenType.TRUE, TokenType.FALSE)
    return new BooleanLiteral(this.currToken, !/* !!... !*/);
    !// ^^^^^^^^^^^^^^
    !// (property) Parser.currToken: {
    !// type: TokenType.TRUE | TokenType.FALSE;
    !// literal: string;
    !// }
    }
    ✅ this.currToken MUST be of type TokenType.TRUE | TokenType.FALSE
    

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84. ! sugarpirate_ " poteto
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    export default function hasOwnProperty(
    obj: T,
    key: PropertyKey
    ): key is keyof T {
    return Object.prototype.hasOwnProperty.call(obj, key);
    }
    

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85. ! sugarpirate_ " poteto
    Just Use Any
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    export default function hasOwnProperty(
    obj: T,
    key: PropertyKey
    ): key is keyof T {
    return Object.prototype.hasOwnProperty.call(obj, key);
    }
    

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86. ! sugarpirate_ " poteto
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    export function lookupIdentifier(ident: string) {
    if (hasOwnProperty(KEYWORDS, ident)) {
    return KEYWORDS[ident];
    }
    return TokenType.IDENT;
    }
    

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87. ! sugarpirate_ " poteto
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    js.la 2020, Los Angeles, CA
    export function lookupIdentifier(ident: string) {
    if (hasOwnProperty(KEYWORDS, ident)) {
    return KEYWORDS[ident];
    }
    return TokenType.IDENT;
    }
    ident starts out
    as a string.
    Cardinality is
    infinite.
    

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88. ! sugarpirate_ " poteto
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    const KEYWORDS = {
    fn: TokenType.FUNCTION,
    let: TokenType.LET,
    true: TokenType.TRUE,
    false: TokenType.FALSE,
    if: TokenType.IF,
    else: TokenType.ELSE,
    return: TokenType.RETURN,
    } as const;
    hasOwnProperty(KEYWORDS, ident)
    

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89. ! sugarpirate_ " poteto
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    js.la 2020, Los Angeles, CA
    export function lookupIdentifier(ident: string) {
    if (hasOwnProperty(KEYWORDS, ident)) {
    return KEYWORDS[ident];
    !// ^^^^^
    !// (parameter) ident:
    !// | "fn"
    !// | "let"
    !// | "true"
    !// | "false"
    !// | "if"
    !// | "else"
    !// | "return"
    }
    return TokenType.IDENT;
    }
    ident is now a
    string literal,
    with a
    cardinality of 7.
    

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90. ! sugarpirate_ " poteto
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    !// inferred by TypeScript
    function lookupIdentifier(
    ident: string
    ):
    | TokenType.IDENT
    | TokenType.FUNCTION
    | TokenType.LET
    | TokenType.TRUE
    | TokenType.FALSE
    | TokenType.IF
    | TokenType.ELSE
    | TokenType.RETURN;
    

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91. ! sugarpirate_ " poteto
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    js.la 2020, Los Angeles, CA
    Recap.
    

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92. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    1. Improve developer
    productivity.
    Making the case for typed JavaScript at Netflix.
    

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93. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    2. Reduce bugs.
    Making the case for typed JavaScript at Netflix.
    

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94. ! sugarpirate_ " poteto
    Just Use Any
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    3. Performance*.
    Making the case for typed JavaScript at Netflix.
    

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95. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    4. End to end type safety.
    Making the case for typed JavaScript at Netflix.
    

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96. ! sugarpirate_ " poteto
    Just Use Any
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    Spend less time
    debugging, and more
    time writing code.
    

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97. ! sugarpirate_ " poteto
    Just Use Any
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    A type is the set of
    possible values for
    a term.
    cardinality · number of elements of the set
    

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98. ! sugarpirate_ " poteto
    Just Use Any
    js.la 2020, Los Angeles, CA
    Less is better.
    

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99. Thank you.
    ! sugarpirate_
    # sugarpirate_
    " poteto
    $ bit.ly/just-use-any-la
    jobs.netflix.com/jobs/870589
    

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