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- ```javascript
- // JavaScript CS
- // convert to string
- // --------------------------------------------------------------------
- let myNumber = 9;
- let myString = String(score);
- // convert to number
- // --------------------------------------------------------------------
- let myString = '44';
- let myNumber = Number(myString);
- // convert to boolean
- // --------------------------------------------------------------------
- let age = 0;
- // good
- let hasAge = Boolean(age);
- // best
- let hasAge = !!age;
- // array map - Array.prototype.map()
- // --------------------------------------------------------------------
- let numbers = [1, 5, 10, 15];
- let doubles = numbers.map(function(x) {
- return x * 2;
- });
- // doubles is now [2, 10, 20, 30]
- // numbers is still [1, 5, 10, 15]
- // es6 example
- let numbers = [2, 4, 8, 10];
- let halves = numbers.map(x => x / 2);
- // halves is now [1, 2, 4, 5]
- // numbers is still [2, 4, 8, 10]
- let numbers = [1, 4, 9];
- let roots = numbers.map(Math.sqrt);
- // roots is now [1, 2, 3]
- // numbers is still [1, 4, 9]
- // array filter - Array.prototype.filter()
- // --------------------------------------------------------------------
- let words = ["spray", "limit", "elite", "exuberant", "destruction", "present", "happy"];
- let longWords = words.filter(function(word){
- return word.length > 6;
- });
- // filtered array longWords is ["exuberant", "destruction", "present"]
- // array find - Array.prototype.find()
- // --------------------------------------------------------------------
- function isBigEnough(element) {
- return element >= 15;
- }
- [12, 5, 8, 130, 44].find(isBigEnough); // 130
- // array slice - Array.prototype.slice()
- // --------------------------------------------------------------------
- let a = ['zero', 'one', 'two', 'three'];
- let sliced = a.slice(1, 3);
- console.log(a); // ['zero', 'one', 'two', 'three']
- console.log(sliced); // ['one', 'two']
- // array splice - Array.prototype.splice()
- // --------------------------------------------------------------------
- let myFish = ['angel', 'clown', 'mandarin', 'sturgeon'];
- myFish.splice(2, 0, 'drum'); // insert 'drum' at 2-index position
- // myFish is ["angel", "clown", "drum", "mandarin", "sturgeon"]
- myFish.splice(2, 1); // remove 1 item at 2-index position (that is, "drum")
- // myFish is ["angel", "clown", "mandarin", "sturgeon"]
- ```
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