前言：
最近看了一些简化JS代码的文章，其中有一篇觉得还不错，但是是英文的，也看了一些中文翻译，一个是一字一句翻译太生硬，没有变成自己的东西，另外就是后面作者有新增没有及时更新，于是我按照自己的语言翻译整理成此文，本文特点以言简意赅为主
当同时声明多个变量时，可简写成一行
//Longhand let x; let y = 20; //Shorthand let x, y = 20;
利用解构，可为多个变量同时赋值
//Longhand let a, b, c; a = 5; b = 8; c = 12; //Shorthand let [a, b, c] = [5, 8, 12];
巧用三元运算符简化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||运算符给变量指定默认值
本质是利用了||运算符的特点，当前面的表达式的结果转成布尔值为false时，则值为后面表达式的结果
//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&&运算符简化if语句
例如某个函数在某个条件为真时才调用，可简写
//Longhand
if (isLoggedin) {
goToHomepage();
}
//Shorthand
isLoggedin && goToHomepage();
使用解构交换两个变量的值
let x = 'Hello', y = 55; //Longhand const temp = x; x = y; y = temp; //Shorthand [x, y] = [y, x];
适用箭头函数简化函数
//Longhand
function add(num1, num2) {
return num1 num2;
}
//Shorthand
const add = (num1, num2) => num1 num2;
需要注意箭头函数和普通函数的区别
使用字符串模板简化代码
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简化
//Longhand
console.log('JavaScript, often abbreviated as JS, is a\n'
'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.`
);
对于多值匹配，可将所有值放在数组中，通过数组方法来简写
//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对象的简洁语法
例如：当属性名和变量名相同时，可直接缩写为一个
let firstname = 'Amitav';
let lastname = 'Mishra';
//Longhand
let obj = {firstname: firstname, lastname: lastname};
//Shorthand
let obj = {firstname, lastname};
使用一元运算符简化字符串转数字
//Longhand
let total = parseInt('453');
let average = parseFloat('42.6');
//Shorthand
let total = '453';
let average = '42.6';
使用repeat()方法简化重复一个字符串
//Longhand
let str = '';
for(let i = 0; i < 5; i ) {
str = 'Hello ';
}
console.log(str); // Hello Hello Hello Hello Hello
// Shorthand
'Hello '.repeat(5);
// 想跟你说100声抱歉！
'sorry\n'.repeat(100);
使用双星号代替Math.pow()
//Longhand const power = Math.pow(4, 3); // 64 // Shorthand const power = 4**3; // 64
使用双波浪线运算符（~~）代替Math.floor()
//Longhand const floor = Math.floor(6.8); // 6 // Shorthand const floor = ~~6.8; // 6
需要注意，~~仅适用于小于2147483647的数字
巧用扩展操作符（...）简化代码
简化数组合并
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]
单层对象的拷贝
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};
寻找数组中的最大和最小值
// Shorthand const arr = [2, 8, 15, 4]; Math.max(...arr); // 15 Math.min(...arr); // 2
使用for in和for of来简化普通for循环
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]);
}
简化获取字符串中的某个字符
let str = 'jscurious.com'; //Longhand str.charAt(2); // c //Shorthand str[2]; // c
移除对象属性
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)过滤掉数组成员的值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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