SOURCE

//字符串反转
let str="asdfghj"
let str2 = str.split("").reverse().join("")
//console.log(str2)
let _str=""
for(let i of str){
    _str=i+_str
     
}
console.log(_str)


//数组中值出现的次数
let arr = [1,1,2,3,4,5,5,5,5,5]
 let obj={}
 for(let i of arr){
     if(obj[i]){
         obj[i]++
     }else{
         obj[i]=1
     }
 }
 console.log(obj)

//按年龄分组
let arr1 =[
    {
        name:'Alice',age:18,sex:'Lfemale'
    },
     {
        name:'Bob',age:18,sex:'Lfemale'
    },
     {
        name:'Eva',age:20,sex:'Lfemale'
    },
     {
        name:'Elly',age:23,sex:'Lfemale'
    },
     {
        name:'Kobe',age:25,sex:'Lfemale'
    }
]
let obj1={}
for(let item of arr1){
    let key = item.age
    if(!obj1[key]){
        obj1[key]=[]
    }
    obj1[key].push(item)
}
   console.log(obj1)


   //多维数组转一维数组
 let _arr =[1,2,[2,3,4,[5,6]]]
 function flarArrry(arr){
        while (arr.some(item => Array.isArray(item))){
           arr = [].concat(...arr)
        }
        console.log(arr)
        return arr
}
this.flarArrry(_arr)