JSNation 2019: Stop the Software Apocalypse with Functional Programming

With the rise of software-based innovation, the business rules and flow controls are getting more complex. Software engineers do not only have to handle increasingly complicated problems, but they also carry greater responsibility for ensuring the quality of their code.

It’s clear that our tools and methods should evolve to build robust software. In this talk, we’ll explore how to leverage functional programming techniques to reduce the complexity and write safer JavaScript in a real-world scenario. Come to see what’s exciting about static analysis, pure functions, composition and immutability; and how these principles are a powerful tool to optimize your code for correctness.

Transcript

1. Stop the Software
   Apocalypse with
   Functional Programming
   

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2. Somers, J. (2017). The Coming Software Apocalypse. The Atlantic.
   

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5. Reduce complexity
   with pure functions
   

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6. Mutability
   let counter = x + 3;
   // counter = 7
   console.log(counter + x);
   // 25
   

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7. let counter = x + 3;
   // counter = 7
   console.log(counter + x);
   // 25
   Where is x
   changing?
   Side effects
   

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8. ?
   

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9. No side effects
   function getX(value) {
   return value + 2;
   }
   getX(2);
   // 4
   getX(5);
   // 7
   

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10. function getX(value) {
    return value + 2;
    }
    getX(2);
    // 4
    getX(5);
    // 7
    No mutation
    Different
    input
    

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11. Optimize for
    correctness
    

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12. Tests
    describe("...", function() {
    beforeEach(function() {
    // prepare the state
    });
    context("when...", function() {
    it("returns...", function() {
    // expects something
    });
    });
    afterEach(function() {
    // clean the state
    });
    });
    

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13. Tests
    describe("...", function() {
    context("when value is 2", function() {
    it("returns...", function() {
    return expect(getX(2)).to.be.equal(4);
    });
    });
    });
    

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14. Types
    function changeProperty(property) {
    return property.toUpperCase();
    }
    const user = {
    name: "Joe",
    age: 50
    };
    

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15. Types
    function changeProperty(property) {
    return property.toUpperCase();
    }
    const user = {
    name: "Joe",
    age: 50
    };
    changeProperty(user.email)
    

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16. Types
    changeProperty(user.email)
    

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17. Types
    interface User {
    name: string;
    age: number;
    }
    function changeProperty(property: string): string {
    return property.toUpperCase();
    }
    const user: User = {
    name: "Joe",
    age: 50
    }
    

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18. Types
    changeProperty(user.email)
    

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19. Structure our
    systems to be more
    comprehensible
    

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20. Thank you!
    @feru
    

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