1、合并数组
正常代码：

let apples = ['redApple', 'greenApple'];
let fruits = ['watermelon', 'strawberry', 'grape'].concat(apples);

console.log( fruits );
//=> ["watermelon", "strawberry", "grape", "redApple", "greenApple"];

修改后的代码：

let apples = ['redApple', 'greenApple'];
let fruits = ['watermelon', 'strawberry', 'grape', ...apples];  // <-- here

console.log( fruits );
//=> ["watermelon", "strawberry", "grape", "redApple", "greenApple"];

let apples = ['redApple', 'greenApple'];
let fruits = [...apples, 'banana', 'cherry'];  // <-- here

console.log( fruits );
//=> ["redApple", "greenApple", "banna", "cherry"];

2、 从数组中获取值

正常代码：

let apples = ['redApple', 'greenApple'];
let redApple = apples[0];
let greenApple = apples[1];

console.log( redApple );    //=> redApple
console.log( greenApple );  //=> greenApple;

使用数组解构的干净代码：

let apples = ['redApple', 'greenApple'];
let [redApple, greenApple] = apples;  // <-- here

console.log( redApple );    //=> redApple
console.log( greenApple );  //=> greenApple;

3、从对象中获取价值

正常代码：

let user = {
  "name": "SJAY",
  "age": 18
}

let name = user.name
let age = user.age

console.log( name ); // => SJAY
console.log( age );  // => 18

使用对象解构的干净代码：

let user = {
  "name": "SJAY",
  "age": 18
}

let {name, age} = user

console.log( name ); // => SJAY
console.log( age ); // => 18

4、循环数组

正常代码：

let fruits = ['watermelon', 'strawberry', 'grape', 'redApple'];

for (let i = 0; i < fruits.length; i++){
  console.log(fruits[i])
};

使用 for of 后的代码：

let fruits = ['watermelon', 'strawberry', 'grape', 'redApple'];

for (fruit of fruits) {
  console.log(fruit)
};

5、使用箭头函数作为回调

正常代码：

let fruits = ['watermelon', 'strawberry', 'grape', 'redApple'];

// Using forEach method
fruits.forEach(function(fruit){
  console.log( fruit );
});

使用箭头函数清理代码：

let fruits = ['watermelon', 'strawberry', 'grape', 'redApple'];
fruits.forEach(fruit => console.log( fruit ));

注意：在处理这个时，箭头函数与普通函数不同。如果你在你的函数中使用它，不要贸然替换它。

6、在数组中查找一项

假设我们需要通过一个对象的属性从一个对象数组中查找一个对象，我们通常使用 for 循环：

let inventory = [
  {name: 'Bananas', quantity: 5},
  {name: 'Apples', quantity: 10},
  {name: 'Grapes', quantity: 2}
];

// Get the object with the name `Apples` inside the array
function getApples(arr, value) {
  for (let index = 0; index < arr.length; index++) {

    // Check the value of this object property `name` is same as 'Apples'
    if (arr[index].name === 'Apples') {  //=> redApple

      // A match was found, return this object
      return arr[index];
    }
  }
}

let result = getApples(inventory);
console.log( result )
//=> { name: "Apples", quantity: 10 };

使用 array.find() 清理代码：

let inventory = [
  {name: 'Bananas', quantity: 5},
  {name: 'Apples', quantity: 10},
  {name: 'Grapes', quantity: 2}
];

// Get the object with the name `Apples` inside the array
function getApples(arr, value) {
  return arr.find(obj => obj.name === 'Apples');  // <-- here
}

let result = getApples(inventory);
console.log( result )
//=> { name: "Apples", quantity: 10 };

7、将字符串转换为数字

正常代码：

let num = parseInt("10")

console.log( num )         //=> 10
console.log( typeof num )  //=> "number";

通过在字符串前添加 + 来清理代码：

let num = +"10";

console.log( num ) //=> 10
console.log( typeof num ) //=> "number"
console.log( +"10" === 10 ) //=> true;

8、检查无效

在使用变量之前，我们经常需要检查其值是否为空。

正常的方法是使用 if-else。

function getUserRole(role) {
let userRole;

// If role is not falsy value
// set userRole as passed role value
if (role) {

userRole = role;

} else {

// else set the `userRole` as USER
userRole = 'USER';

}

return userRole;
}

console.log( getUserRole() ) //=> "USER"
console.log( getUserRole('ADMIN') ) //=> "ADMIN";

使用 || 清理代码 ：

function getUserRole(role) {
return role || 'USER'; // <-- here
}

console.log( getUserRole() ) //=> "USER"
console.log( getUserRole('ADMIN') ) //=> "ADMIN";

9、字符串连接

正常代码：

let name = 'bytefish';
let message = 'Hi '+ name + '!';

使用模板文字清洁代码：

let name = 'bytefish';
let message = `Hi ${name}!`;

10、使用速记

正常代码：

let x = 1

if (x !== '' && x !== null && x !== undefined) {
  console.log('x is not nullish')
};

使用速记运算符清洁代码：

let x = 1

if (!!x){
  console.log('x is not nullish')
};