You Won’t Believe This One Weird Way to Rewrite Closures

Closures are undoubtedly the most powerful feature JavaScript inherited from its Lisp forbears. But would JS be so powerful… without them?

We’ll reimplement closures entirely from scratch without the convenience of native local variables or function parameters. Entirely in JavaScript. Using prototypal inheritance, some clever hat-tips from graphics programming, amnesic function bodies, and this one weird global variable.

https://github.com/nybblr/closures

Transcript

1. You won’t believe
   this one weird way
   to rewrite closures.
   TL;DR waste of nanoseconds
   { };
   

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2. This talk on #JS
   will restore your
   faith in closures!
   A.K.A.
   { };
   

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3. One weird Nerd.
   Jonathan Martin
   We Teach. We Develop. We Write.
   

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4. closure() ===
   scope + statements;
   

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5. They survived w/o
   closures, and the
   results are shocking!
   

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6. FORTRAN 77: 501 FORMAT(3I5)

   602 FORMAT("NORMAL END")

   603 FORMAT("INPUT ERROR OR ZERO VALUE ERROR")

   INTEGER A,B,C

   10 READ(5,501,END=50,ERR=90) A,B,C

   IF(A=0 .OR. B=0 .OR. C=0) GO TO 90

   S = (A + B + C) / 2.0

   AREA = SQRT( S * (S - A) * (S - B) * (S - C))
   WRITE(6,601) A,B,C,AREA

   GO TO 10

   50 WRITE(6,602)

   STOP

   90 WRITE(6,603)

   STOP

   END
   {
   

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7. x86 Assembly: section .data

   str: db 'Hello world!', 0Ah

   str_len: equ $ - str

   

   section .text

   global _start

   

   _start:

   mov eax, 4

   mov ebx, 1

   

   mov ecx, str

   mov edx, str_len

   int 80h

   

   mov eax, 1

   mov ebx, 0

   int 80h
   {
   

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8. Ruby: class Dog

   def bark

   puts "Bowowowow!"

   end

   end

   

   Cat = Class.new

   Cat.send(:define_method,

   :bark, Dog.instance_method(:bark))

   # => TypeError: bind argument
   must be a subclass of Dog

   

   Cat.new.bark

   # => NoMethodError: undefined method
   `bark' for Cat:Class
   {
   

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9. Convert a method to a lambda in Ruby:
   lambda(&method(:events_path))
   OR JUST USE JAVASCRIPT.
   @deisinger
   “
   “
   

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10. This stay-at-home
    developer built his
    own closures!
    

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11. Do these 5 things
    every line.
    function params, var, variable assignment
    function memoization
    one global variable
    amnesic function bodies
    shortcut local variables
    ✗
    ✗
    ✓
    ✓
    ✓
    

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12. Use this code, never
    run slow #JS again!
    var local = 'Variable';
    console.log(local);
    var func = function(arg1, arg2, arg3) {

    // ...

    };
    

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13. Use this code, never
    run slow #JS again!
    s('local', 'Variable');
    console.log(g('local'));
    f('func', ['arg1', 'arg2', 'arg3'], function(){

    // ...

    });
    ⇢
    ⇢
    ⇢
    

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14. Your code can look…
    var outer = function (x, y) {

    var inner = function (x, z) {

    return [x, y, z];

    };

    return inner;

    };

    

    console.log(outer(1,2)(3,4));
    

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15. …like this!
    f('outer', ['x', 'y'], function () {

    f('inner', ['x', 'z'], function () {

    return [g('x'), g('y'), g('z')];

    });

    return g('inner');

    });

    

    console.log(g('outer')(1,2)(3,4));
    

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16. These 70 lines will
    blow your mind. Ruby
    developers HATE IT!
    

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17. He wrote a transpiler.
    What happens next
    will make you weep.
    github.com/nybblr/closures
    

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19. Prototype-destroying
    developer is the most
    satisfying thing you’ll
    see today!
    The Future™
    { };
    

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20. Thanks!
    @nybblr
    

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