本篇文章給大家整理分享了20個提升效率的JavaScript簡寫技巧，希望對大家有幫助。

簡寫技巧

當(dāng)同時聲明多個變量時，可簡寫成一行

//Longhand let x; let y = 20;   //Shorthand let x, y = 20;

利用解構(gòu)，可為多個變量同時賦值

//Longhand let a, b, c; a = 5; b = 8; c = 12; //Shorthand let [a, b, c] = [5, 8, 12];

巧用三元運(yùn)算符簡化if else

//Longhand  let marks = 26;  let result;  if (marks >= 30) {    result = 'Pass';  } else {     result = 'Fail';  }  //Shorthand  let result = marks >= 30 ? 'Pass' : 'Fail';

使用||運(yùn)算符給變量指定默認(rèn)值

本質(zhì)是利用了||運(yùn)算符的特點(diǎn)，當(dāng)前面的表達(dá)式的結(jié)果轉(zhuǎn)成布爾值為false時，則值為后面表達(dá)式的結(jié)果

//Longhand let imagePath; let path = getImagePath(); if (path !== null && path !== undefined && path !== '') {     imagePath = path; } else {     imagePath = 'default.jpg'; } //Shorthand let imagePath = getImagePath() || 'default.jpg';

使用&&運(yùn)算符簡化if語句

例如某個函數(shù)在某個條件為真時才調(diào)用，可簡寫

//Longhand if (isLoggedin) {     goToHomepage();  } //Shorthand isLoggedin && goToHomepage();

使用解構(gòu)交換兩個變量的值

let x = 'Hello', y = 55; //Longhand const temp = x; x = y; y = temp; //Shorthand [x, y] = [y, x];

適用箭頭函數(shù)簡化函數(shù)

//Longhand function add(num1, num2) {   return num1 + num2; } //Shorthand const add = (num1, num2) => num1 + num2;

需要注意箭頭函數(shù)和普通函數(shù)的區(qū)別

使用字符串模板簡化代碼

使用模板字符串代替原始的字符串拼接

//Longhand console.log('You got a missed call from ' + number + ' at ' + time); //Shorthand console.log(`You got a missed call from ${number} at ${time}`);

多行字符串也可使用字符串模板簡化

//Longhand console.log('JavaScript, often abbreviated as JS, is an' +              'programming language that conforms to the n' +              'ECMAScript specification. JavaScript is high-level,n' +              'often just-in-time compiled, and multi-paradigm.'             ); //Shorthand console.log(`JavaScript, often abbreviated as JS, is a             programming language that conforms to the             ECMAScript specification. JavaScript is high-level,             often just-in-time compiled, and multi-paradigm.`             );

對于多值匹配，可將所有值放在數(shù)組中，通過數(shù)組方法來簡寫

//Longhand if (value === 1 || value === 'one' || value === 2 || value === 'two') {   // Execute some code } // Shorthand 1 if ([1, 'one', 2, 'two'].indexOf(value) >= 0) {    // Execute some code } // Shorthand 2 if ([1, 'one', 2, 'two'].includes(value)) {      // Execute some code  }

巧用ES6對象的簡潔語法

例如，當(dāng)屬性名和變量名相同時，可直接縮寫為一個

let firstname = 'Amitav'; let lastname = 'Mishra'; //Longhand let obj = {firstname: firstname, lastname: lastname}; //Shorthand let obj = {firstname, lastname};

使用一元運(yùn)算符簡化字符串轉(zhuǎn)數(shù)字

//Longhand let total = parseInt('453'); let average = parseFloat('42.6'); //Shorthand let total = +'453'; let average = +'42.6';

使用repeat()方法簡化重復(fù)一個字符串

//Longhand let str = ''; for(let i = 0; i < 5; i ++) {   str += 'Hello '; } console.log(str); // Hello Hello Hello Hello Hello // Shorthand 'Hello '.repeat(5); // 想跟你說100聲抱歉！ 'sorryn'.repeat(100);

使用雙星號代替Math.pow()

//Longhand const power = Math.pow(4, 3); // 64 // Shorthand const power = 4**3; // 64

使用雙波浪線運(yùn)算符（~~）代替Math.floor()

//Longhand const floor = Math.floor(6.8); // 6 // Shorthand const floor = ~~6.8; // 6

需要注意，~~僅適用于小于2147483647的數(shù)字

巧用擴(kuò)展操作符（…）簡化代碼

簡化數(shù)組合并

let arr1 = [20, 30]; //Longhand let arr2 = arr1.concat([60, 80]); // [20, 30, 60, 80] //Shorthand let arr2 = [...arr1, 60, 80]; // [20, 30, 60, 80]

單層對象的拷貝

let obj = {x: 20, y: {z: 30}}; //Longhand const makeDeepClone = (obj) => {   let newObject = {};   Object.keys(obj).map(key => {       if(typeof obj[key] === 'object'){           newObject[key] = makeDeepClone(obj[key]);       } else {           newObject[key] = obj[key];       } }); return newObject; } const cloneObj = makeDeepClone(obj); //Shorthand const cloneObj = JSON.parse(JSON.stringify(obj)); //Shorthand for single level object let obj = {x: 20, y: 'hello'}; const cloneObj = {...obj};

尋找數(shù)組中的最大和最小值

// Shorthand const arr = [2, 8, 15, 4]; Math.max(...arr); // 15 Math.min(...arr); // 2

使用for in和for of來簡化普通for循環(huán)

let arr = [10, 20, 30, 40]; //Longhand for (let i = 0; i < arr.length; i++) {   console.log(arr[i]); } //Shorthand //for of loop for (const val of arr) {   console.log(val); } //for in loop for (const index in arr) {   console.log(arr[index]); }

簡化獲取字符串中的某個字符

let str = 'jscurious.com'; //Longhand str.charAt(2); // c //Shorthand str[2]; // c

移除對象屬性

let obj = {x: 45, y: 72, z: 68, p: 98}; // Longhand delete obj.x; delete obj.p; console.log(obj); // {y: 72, z: 68} // Shorthand let {x, p, ...newObj} = obj; console.log(newObj); // {y: 72, z: 68}

使用arr.filter(Boolean)過濾掉數(shù)組成員的值falsey

let arr = [12, null, 0, 'xyz', null, -25, NaN, '', undefined, 0.5, false]; //Longhand let filterArray = arr.filter(function(value) {     if(value) return value; }); // filterArray = [12, "xyz", -25, 0.5] // Shorthand let filterArray = arr.filter(Boolean); // filterArray = [12, "xyz", -25, 0.5]

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