代码简洁之道

根据条件给变量赋值布尔值

// bad
if(arr.includes("xxx")){
    has = true;
}else {
    has = false;
}

// good
has = arr.includes("xxx");

根据数组有无内容做什么

// bad
if(arr.length !== 0){
    // todo
}

if(arr.length == 0){
    // todo
}

// good
if(arr.length){
    // todo
}

if(!arr.length){
    // todo
}

单变量多可能值判断

// bad
if(a == 1 || a == 2 || a == 3 || a == 4){
    // todo
}

// good
var arr = [1,2,3,4];
if(arr.includes(a)){
    // todo
}

快速获取所有对象的属性名或者属性值

var obj = {
    name: "obj",
    age: 212,
    tel: "123342"
};

// 获取对象的属性名组成的数组
Object.getOwnPropertyNames(obj); // ["name", "age", "tel"]
Object.keys(obj); // ["name", "age", "tel"]


// 获取对象的属性值组成的数组
Object.values(obj); // ["obj", 212, "123342"]

解构赋值进行变量替换

var a = 10, b = 20;

// bad
var temp = a;
a = b;
b = temp;

// good
[b, a] = [a, b];

解构简化函数参数长属性名

// bad
setForm (data) {
    this.one = data.user_info_detail_name;
    this.two = data.address_detail_name;
}
// good
setForm ({user_info_detail_name, address_detail_name}) {
    this.one = user_info_detail_name;
    this.two = address_detail_name;
}

// best
setForm ({user_info_detail_name: one, address_detail_name: two}) {
    this.one = one;
    this.two = two;
}

对象中的可选属性

const obj = {
    a: "whatever"
}
if(b){
    obj.c = "ok";
}

// best
const obj = {
    a: "whatever",
    ...(b && { c: "ok" })
}

函数默认值

// bad
function sum(a, b){
    if(a === undefined){
        a = 0;
    }
    if(b === undefined){
        b = 0;
    }
}

// good
function sum(a, b){
    a = a || 0;
    b = b || 0;
}

// best
function sum(a = 0, b = 0){

}

调用对象的属性的属性

有时候可能对象的属性不是一个对象，直接获取就会报错，需要验证有值

var user = {
    name: "李白"
    friend: {
        name: "杜甫"
    }
}

// bad
var friendName = user.friend.name

// good
var friendName = user.friend && user.friend.name

函数参数校验

function(a, b){
    if(!a){
        throw new Error("请传入必要的参数");
    }

}

// good
function checkNull(){
    throw new Error("请传入必要的参数");
}
function(a = checkNull(), b){

}

计算字符串中某个字符的出现次数

const charTotals = arr => arr.reduce((totals, char) => ({
    ...totals, [char]: (totals[char] || 0) + 1
}), {})

charTotals("happy".split(""));
// "h":1,"a":1,"p":2,"y":1