JS New Features declared at Google IO 2019

JS-New-Features-Google-IO-2019.js

/**
* 1. String.matchAll()
* The matchAll() method returns an iterator of all results matching a string against a
* regular expression, including capturing groups.
*
* URL - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/matchAll
*/


/**
* 2. Numeric Separtor
* http://2ality.com/2018/02/numeric-separators.html
* http://exploringjs.com/es2016-es2017/ch_tc39-process.html
*/
1_234_567_890_123_456_789n

/**
 * 3. BigInt
 * https://tc39.github.io/proposal-bigint/#sec-bigint.prototype.tolocalestring
 */

//Example why BigInt is Useful
1234567890123456789 * 123
// Output - 151851850485185200000 X

1234567890123456789n * 123n
// Output - 151851850485185185047n

12345678901234567890n.toLocaleString("en");
// Output - 12,345,678,901,234,567,890

const formatter = new Intl.NumberFormat('en');
formatter.format(12_345_678_901_234_567_890n);
// Output - 12,345,678,901,234,567,890


/**
 * 4. Async/Await
 * Top Level Await
 */
async function test() {
    const result = await doAsync();

    // Use result here
}
// No use of async as per google proposal
const result = await doAsync();


/**
 * 5. Promise.allSettled & Promise.any
 */

const promises = [
    asyncFunc1(),
    asyncFunc2(),
    asyncFunc3()
]

try {
    const result = await Promise.all(promises);
    doSomething(result);
} catch (error) {
    showError(error);
}


try {
    const result = await Promise.race(promises);
    doSomething(result);
} catch (error) {
    showError(error);
}

try {
    const result = await Promise.allSettled(promises);
    doSomething(result);
} catch (error) {
    showError(error);
}

try {
    const result = await Promise.any(promises);
    doSomething(result);
} catch (error) {
    showError(error);
}



/**
 * 6. Private & Public property in Class
 * Use of Class Field
 */
class Person {
    constructor() {
        this._name = "Ajay";
    }
}

class Person {
    name = "Ajay";
}


// Use of Private Variable/Property
class Person {
    #name = "Ajay";

    print() {
        console.log(this.#name);
    }
}


// Old
class Person {
    constructor(name) {
        this.name = name;
    }
}

// Old 
class Student extends Person {
    constructor(name) {
        super(name);

        this.study = true
    }
}

class Student extends Person {
    study = true;
}

/**
 * 7. globalThis
 * a variable to get the global this irrespective of the environment
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/globalThis
 */
//on browser
console.log(globalThis);


/**
 * 8. Stable Sort
 */

const arr = [
    { name: "Test 1", "total_marks": 80 },
    { name: "Test 2", "total_marks": 70 },
    { name: "Test 3", "total_marks": 90 },
    { name: "Test 32", "total_marks": 90 },
];

arr.sort((a, b) => b.total_marks - a.total_marks);

//Output
[
    { name: "Test 2", "total_marks": 70 },
    { name: "Test 1", "total_marks": 80 },
    { name: "Test 3", "total_marks": 90 },
    { name: "Test 32", "total_marks": 90 },
];


/**
 * 9. flat && flatMap()
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flatMap
 */
const arr = [1, [2, [3]]];
console.log(arr.flat(Infinity));
// [1,2,[3]]


const arrr1 = [1, 2, 3];
const doubleArr1 = arr1.map(x => [x, x]);

// [[1,1],[2,2],[3,3]]

doubleArr1.flat();
//[1,1,2,2,3,3]


arrr1.flatMap(x => [x, x]);


/**
 * 10. Object.fromEntries
 */
const obj = { name: "Ronit", age: 28 };
Object.defineProperties()