JavaScript: Past, Present, and Future - NDC Porto 2020

Transcript

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12. > const lol = a + b + c – f * ( n + o );
    NaN
    

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13. > NaN >= 0
    false
    

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14. > NaN <= 0
    false
    

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15. > typeof NaN
    number
    

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16. ( a + b ) + c = a + ( b + c ) // mathematically true
    > 0.1 + 0.2 === 0.3
    false
    > ( a + b ) + c == a + ( b + c )
    ??
    

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17. > 0.1 + 0.2
    0.30000000000000004
    

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18. > Math.round(0.4999999999999999722444243843710864894092082)
    0
    > Math.round(0.4999999999999999722444243843710864894092083)
    1
    I’ve got 99 problems but
    JavaScript ain’t
    1.0000000000000009
    

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19. > [ 2, 10 ].sort()
    [ 10, 2 ]
    

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20. > ['10','10','10', '10', '10'].map( parseInt )
    [ 10, NaN, 2, 3, 4 ]
    

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21. > typeof undefined // undefined
    > typeof true // boolean
    > typeof "hello" // string
    > typeof 1 // number
    > typeof {lol:true} // object
    > typeof [1,2,3] // object
    > typeof null // object
    

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22. > null == 0 // false
    > null > 0 // false
    > null < 0 // false
    > null >= 0 // true
    > null <= 0 // true
    > Number( null ) // 0
    

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23. > false
    > null
    > undefined
    > ""
    > 0
    > NaN
    

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24. > wat.test("javascript"); // true
    > wat.test("wat r u doin"); // false
    > const wat = /a/g;
    

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25. // undefined
    function troll() {
    return
    {
    haha: "ha!"
    };
    }
    troll();
    // automatic semi-colon
    

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26. const arr = [];
    arr[1] = 1;
    arr[3] = 2;
    arr[10] = 3;
    arr.length // 11
    arr[-1] = 4;
    arr.s = 5;
    arr.length // 11
    

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96. const user1 = {
    firstName: "David",
    lastName: "Neal",
    address: {
    street: "123 Main Street",
    city: "Nashville",
    state: "Tennessee"
    }
    };
    

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97. const user1 = {
    firstName: "David",
    lastName: "Neal",
    address: {
    street: "123 Main Street",
    city: "Nashville",
    state: "Tennessee"
    }
    };
    const city = user1?.address?.zipCode;
    

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99. const v1 = falseyNullOrUndefined || "defaultValue";
    

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100. const v1 = falseyNullOrUndefined || "defaultValue";
     const v2 = onlyNullOrUndefined ?? "defaultValue";
     

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101. globalThis = window ?? self ?? global;
     

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102. Promise.all() –or- Promise.allSettled()
     

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103. let config;
     if (production) {
     config = await import("./config.production.js");
     }
     reportBtn.addEventListener("click", async () => {
     const reporter = await import("./reporter.js);
     reporter.generateReport();
     });
     

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104. const integers = Array.from(html.matchAll(/[0-9]*/g));
     

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105. const big = BigInt(Number.MAX_SAFE_INTEGER);
     const big2 = 9007199254740991n;
     const evenBigger = big + 3000000n;
     

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109. To boldly go where NaN has
     undefined before!
     

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116. Mobile Apps
     Automation / DevOps
     Command Line (CLI)
     Services
     

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