JavaScript一些常用 API整理匯總

const arr = [3,4,4,5,4,6,5,7];console.log(new Set(arr)); // {3,4,5,6,7}const a = Array.from(new Set(arr)) // [3, 4, 5, 6, 7]//或者const a = [...new Set(arr)]//推薦

const arr = [1,2,3,4,5,6];console.log(arr.sort((a,b)=>a-b)) // [1,2,3,4,5,6] 大小正序cosole.log(arr.sort((a,b)=>b-a))// [6,5,4,3,2,1] 大小倒序//不可以進(jìn)行運(yùn)算的則比較編碼大小  'b' > 'a' => true

const arr = [3,4,4,5,4,6,5,7];conosle.log(arr.reverse());  // [7, 6, 5, 5, 4, 4, 4, 3]

//數(shù)組const arr = [0,1,2];delete arr[1];conosle.log(arr); // [0, empty, 2]

//對(duì)象const obj = {name: '謝大腳',age: '18',sex: '女'};delete obj.sex;console.log(obj); // {name: "謝大腳", age: "18"}

const arr = [0,1,2];const a = arr.shift(); // 0console.log(arr); // [1, 2]

const arr = [3,4,4,5,4,6,5,7];const a = arr.unshift(8);console.log(a); // 9(a為返回的數(shù)組的新長(zhǎng)度)console.log(arr); // [8, 3, 4, 4, 5, 4, 6, 5, 7]

const arr = [3,4,4,5,4,6,5,7];const a = arr.push(8,9);console.log(a); // 10(a為返回的數(shù)組的新長(zhǎng)度)console.log(arr); // [3, 4, 4, 5, 4, 6, 5, 7, 8, 9]

const arr = [3,4,4,5,4,6,5,7];console.log(arr.toString()); // 3,4,4,5,4,6,5,7

//數(shù)組const a = [1,2,3];const b = [4,5];const c = a.concat(b); // [1, 2, 3, 4, 5]

//字符串const x = 'abc';const y = 'def';const z = x.concat(y); // abcdef

const arr = [3,4,4,5,4,6,5,7];console.log(arr.join('-')); // 3-4-4-5-4-6-5-7

//數(shù)組const arr = [3,4,4,5,4,6,5,7];const a = arr.slice(2, 5); // [4, 5, 4]

//字符串const x = 'abcdefgh';const y = x.slice(3, 6); // def

const arr = [3,4,4,5,4,6,5,7];const a = arr.splice(3, 2, 12); // [5, 4]console.log(arr); // [3, 4, 4, 12, 6, 5, 7]

const arr = [3,4,4,5,4,6,5,7];const a = arr.map(item => item*2;) // [6, 8, 8, 10, 8, 12, 10, 14]

const arr = [3,4,4,5,4,6,5,7];arr.forEach(function(item,index,arr){console.log(value)}))  3  4  4  5  4  6  5  7

// 對(duì)象const obj = {a: 123, b: 12, c: 2 };for (let a in obj) {    console.log(a)}// a   b   c   //數(shù)組const arr = [3,4,4,5];for(let a in arr) {    console.log(a)}// 0   1   2   3

const arr = [3,4,4,5,4,6,5,7];const a = arr.filter(item => item % 3 > 1);console.log(a); // [5, 5]

const arr = [3,4,4,5,4,6,5,7];

console.log( arr.some( function( item, index, array ){     console.log( 'item=' + item + ',index='+index+',array='+array );     return item > 3; }));//  item=3,index=0,array=3,4,4,5,4,6,5,7//   item=4,index=1,array=3,4,4,5,4,6,5,7//   true

console.log( arr.every( function( item, index, array ){     console.log( 'item=' + item + ',index='+index+',array='+array );     return item > 3; }));// item=3,index=0,array=3,4,4,5,4,6,5,7//false

reduce（() => (pre, cur, curIndex, arr), initialValue）

//數(shù)組const arr = [3,4,4,5,4,6,5,7];console.log(arr.indexOf(4)) // 1console.log(arr.indexOf('4'))  // -1

//字符串const string = 'asdfghj';console.log(string.indexOf('a')) // 0lastIndexOf（）

const arr = [3,4,4,5,4,6,5,7];console.log(arr.lastIndexOf(4)) // 4(從左到右數(shù)最后出現(xiàn)的位置，字符串同理)

const arr = [[1,2,3],[4,5,[6,7]]];const a = arr.flatten(3);console.log(a); // [1, 2, 3, 4, 5, 6, 7]

const arr = [3,4,4,5,4,6,5,7];console.log(Array.isArray(arr)) // true

const arr = [3,4,4,5,4,6,5,7];const a = test.find(item => item > 3);console.log(a); //4(find() 方法返回通過(guò)測(cè)試（函數(shù)內(nèi)判斷）的數(shù)組的第一個(gè)元素的值。)

const b = test.find(item => item == 0);console.log(b); //undefined(如果沒(méi)有符合條件的元素返回 undefined)

const str = 'hello guys';console.log(str.charAt(3))  // 1

const str = 'hello guys';console.log(str.charCodeAt(3))  // 111

const str = 'hello guys';console.log(str.match('guys'))  // ["guys"]

// 使用正則匹配字符串const strs = '1.hello guys, 2.are you ok?';console.log(strs.match(/\d+/g)) // ["1", "2"]

const str = 'hello guys';console.log(str.replace('guys', 'man'))  // hello man

const str = 'AA_BB_CC.bin';console.log(str.replace(/[^\_]/g),'')  // __(兩個(gè)下劃線)

const str = 'hello guys';console.log(str.search('guys'))  // 6console.log(str.indexOf('guys'))  // 6// 區(qū)別const string = 'abcdefg.1234';console.log(string.search(/\./)) // 7（轉(zhuǎn)譯之后可以匹配到 . 的位置）console.log(string.indexOf(/\./)) // -1 （相當(dāng)于匹配/\./，找不到則返回-1,只能匹配字符串）

const str = 'hello guys';console.log(str.split('')) // ["h", "e", "l", "l", "o", " ", "g", "u", "y", "s"] console.log(str.split('', 3)) //  ["h", "e", "l"]

const str = 'hello guys';console.log(str.toLocaleLowerCase())  // hello guysconsole.log(str.toLowerCase())  //  hello guys

const str = 'hello guys';console.log(str.toLocaleUpperCase())  // HELLO GUYSconsole.log(str.toUpperCase())  // HELLO GUYS

const str = 'hello guys';console.log(str.substr(2))  // llo guysconsole.log(str.substr(2, 7))  // llo guy

const str = 'hello guys';console.log(str.substring(2))   // llo guysconsole.log(str.substring(2, 7))  //  llo g

const str = '    hello guys    ';console.log(str.trim()) // hello guys(不會(huì)改變?cè)瓟?shù)組)

const str = '{"name": "phoebe", "age": 20}';const obj = JSON.parse(str)  // {name: "phoebe", age: 20}（object類型）

const obj = {"name": "Tins", "age": 22};const str = JSON.stringify(obj)  // {"name":"Tins","age":22}(string類型)

ObjectrType.prototype.valueOf = function() { return customValue; };

ObjectrType.valueOf()

function Dog(name) {  this.name = name;}

const dog1 = new Dog('Gabby');

Dog.prototype.toString = function dogToString() {  return '' + this.name;}

console.log(dog1.toString());  // Gabby

let foo = {};foo.toLocaleString(); // "[object Object]"

const arr = [];

Array.prototype.isPrototypeOf(arr); // true

// 修改obj的原型Object.setPrototypeOf(arr, String.prototype);Array.prototype.isPrototypeOf(arr); // falseString.prototype.isPrototypeOf(arr); // true

let obj = {};// 定義一個(gè)object實(shí)例obj.prop1 = 'value1'; // prop1是一個(gè)自有屬性obj.constructor.prototype.prop2 = 'value2'; // prop2是一個(gè)原型鏈屬性// 無(wú)論自有屬性還是原型鏈屬性，我們都可以訪問(wèn)到console.info(obj.prop1); // value1console.info(obj.prop2); // value2// 使用`hasOwnProperty()`方法判斷屬性是否為自有屬性obj.hasOwnProperty('prop1'); // trueobj.hasOwnProperty('prop2'); // false

const obj = { name: 'ecmaer'};

Object.getOwnPropertyDescriptor(obj, 'name').enumerable; // trueobj.propertyIsEnumerable('name'); // true

// 將屬性name設(shè)置成不可枚舉Object.defineProperty(obj, 'name', {enumerable: false});obj.propertyIsEnumerable('name'); // false



for(let i in obj){    console.info(obj[i]); // 沒(méi)有遍歷出'ecmaer'}

typeof 123 //numbertypeof '123' //stringtypeof true // booleantypeof false //booleantypeof undefined // undefinedtypeof Math.abs // functiontypeof function () {} // function

// 當(dāng)遇上`null`、`Array`和通常意義上的`object`,都會(huì)返回 objecttypeof null // objecttypeof [] // object（所以判斷數(shù)組時(shí)可以使用Array.isArray(arr)）typeof {} // object

// 當(dāng)數(shù)據(jù)使用了new關(guān)鍵字和包裝對(duì)象以后，數(shù)據(jù)都會(huì)變成Object類型，不加new關(guān)鍵字時(shí)會(huì)被當(dāng)作普通的函數(shù)處理。typeof new Number(123); //'object'typeof Number(123); // 'number'
typeof new Boolean(true); //'object'typeof Boolean(true); // 'boolean'
typeof new String(123); // 'object'typeof String(123); // 'string'

function Car(make, model, year) {  this.make = make;  this.model = model;  this.year = year;}const auto = new Car('Honda', 'Accord', 1998);

console.log(auto instanceof Car); // trueconsole.log(auto instanceof Object); // true

const arrs = [1,2,3];console.log(typeof arrs) // objectconsole.log(Object.Prototype.toString.call(arrs))  // [object Array]

const arr = [2,5,4,7,6]const a = Function.prototype.apply.call(Math.max, null,arr)console.log(a)  // 7

const arr = [2,5,4,7,6]const a = Function.prototype.call.apply(Math.max, arr)console.log(a)  // 7
//如果apply的第二個(gè)參數(shù)是個(gè)null，會(huì)返回-Infinityconst b = Function.prototype.call.apply(Math.max, null, arr)console.log(b)  // -Infinity

const fruits = {    "name": "apple",    getOtherFriut: function() {        return this.name;    }}
const color = {   "name": " is red" }
const fruitColor = fruits.getOtherFriut.bind(this, color)console.log(fruitColor()) //is red

const date = new Date();