SOURCE

// 字符串 数字判空
let str = '';
let num = 0;
console.log(Boolean(str),Boolean(num))
// 数组判空
let arr = [11,22]
console.log(Boolean(arr.length === 0))
console.log(arr.indexOf(22))
// 对象判空
let obj = {a:1, b:2}
console.log(Object.keys(obj).length)
console.log(obj.hasOwnProperty('a'))
// 逻辑运算符 &&
let objL = {name:'x'}
if(objL && objL.name){
    console.log('有 name 字段的情况')
}