1.通过条件判断给变量赋值布尔值的正确姿势
// bad\
if (a === 'a') {\
b = true\
} else {\
b = false\
}\
\
// good\
b = a === 'a'
2.在if中判断数组长度不为零的正确姿势
// bad\
if (arr.length !== 0) {\
// todo\
}\
\
// good\
if (arr.length) {\
// todo\
}\
3.同理，在if中判断数组长度为零的正确姿势
// bad\
if (arr.length === 0) {\
// todo\
}\
\
// good\
if (!arr.length) {\
// todo\
}
4.简单的if判断使用三元表达式
// bad\
if (a === 'a') {\
b = a\
} else {\
b = c\
}\
\
// good\
b = a === 'a' ? a : c
5.使用includes简化if判断
// bad\
if (a === 1 || a === 2 || a === 3 || a === 4) {\
// todo\
}\
\
// good\
let arr = [1, 2, 3, 4]\
if (arr.includes(a)) {\
// todo\
}
6.使用some方法判断是否有满足条件的元素
// bad\
let arr = [1, 3, 5, 7]\
function isHasNum (n) {\
for (let i = 0; i < arr.length; i ++) {\
if (arr[i] === n) {\
return true\
}\
}\
return false\
}\
\
// good\
let arr = [1, 3, 5, 7]\
let isHasNum = n => arr.some(num => num === n)\
\
// best\
let arr = [1, 3, 5, 7]\
let isHasNum = (n, arr) => arr.some(num => num === n)
7.使用forEach方法遍历数组，不形成新数组
// bad\
for (let i = 0; i < arr.length; i ++) {\
// todo\
arr[i].key = balabala\
}\
\
// good\
arr.forEach(item => {\
// todo\
item.key = balabala\
})\
8.使用filter方法过滤原数组，形成新数组
// bad\
let arr = [1, 3, 5, 7],\
newArr = []\
for (let i = 0; i < arr.length; i ++) {\
if (arr[i] > 4) {\
newArr.push(arr[i])\
}\
}\
\
// good\
let arr = [1, 3, 5, 7]\
let newArr = arr.filter(n => n > 4) // [5, 7]
9.使用map对数组中所有元素批量处理，形成新数组
// bad\
let arr = [1, 3, 5, 7],\
newArr = []\
for (let i = 0; i < arr.length; i ++) {\
newArr.push(arr[i] + 1)\
}\
\
// good\
let arr = [1, 3, 5, 7]\
let newArr = arr.map(n => n + 1) // [2, 4, 6, 8]
10.使用Object.values快速获取对象键值
let obj = {\
a: 1,\
b: 2\
}\
// bad\
let values = []\
for (key in obj) {\
values.push(obj[key])\
}\
\
// good\
let values = Object.values(obj) // [1, 2]
11.使用Object.keys快速获取对象键名
let obj = {\
a: 1,\
b: 2\
}\
// bad\
let keys = []\
for (value in obj) {\
keys.push(value)\
}\
\
// good\
let keys = Object.keys(obj) // ['a', 'b']
12.解构数组进行变量值的替换
// bad\
let a = 1,\
b = 2\
let temp = a\
a = b\
b = temp\
\
// good\
let a = 1,\
b = 2\
[b, a] = [a, b]\
13||短路符设置默认值
let person = {\
name: '张三',\
age: 38\
}\
\
let name = person.name || '佚名'
14.路符判断依赖的键是否存在防止报错'xxx of undfined'
let person = {\
name: '张三',\
age: 38,\
children: {\
name: '张小三'\
}\
}\
\
let childrenName = person.children && person.childre.name
15字符串拼接使用${}
let person = {\
name: 'LiMing',\
age: 18\
}\
// bad\
function sayHi (obj) {\
console.log('大家好，我叫' + person.name = '，我今年' + person.age + '了')\
}\
\
// good\
function sayHi (person) {\
console.log(`大家好，我叫${person.name}，我今年${person.age}了`)\
}\
\
// best\
function sayHi ({name, age}) {\
console.log(`大家好，我叫${name}，我今年${age}了`)\
}\
16.用箭头函数
let arr [18, 19, 20, 21, 22]\
// bad\
function findStudentByAge (arr, age) {\
return arr.filter(function (num) {\
return num === age\
})\
}\
\
// good\
let findStudentByAge = (arr, age)=> arr.filter(num => num === age)\
17数参数校验
// bad\
let findStudentByAge = (arr, age) => {\
if (!age) throw new Error('参数不能为空')\
return arr.filter(num => num === age)\
}\
\
// good\
let checkoutType = () => {\
throw new Error('参数不能为空')\
}\
let findStudentByAge = (arr, age = checkoutType()) =>\
arr.filter(num => num === age)
转载自：mp.weixin.qq.com/s/63xQAol1D…
