编辑代码

//-- 每个值的平方
var arr1 = [2, 3, 4, 5, 6]; 
var newArr1=arr1.reduce((result,cur)=>{
    result.push(cur*cur)
    return result
},[])
console.log(newArr1)

//--数组求和
let num=[1,2,3,4,5]
let sumResult = num.reduce((pre,cur,index,self)=>{
    return pre+cur
},0)
console.log(sumResult)
 //--扁平化数组(仅限一维数组)
 let arrayToAttay=[
     1,2,3,[
         2,3,4,[
             5,6,7
         ],[
             3,4,5
         ]
     ],[
         1,1,1
     ],1,1,1
 ]
 let arrayToUniq = arrayToAttay.reduce((pre,next,index,self)=>{
     console.log(next)
     return pre.concat(next)
 },[])
 console.log(arrayToUniq)

 //--字符串每个元素的个数
 let str="huhkjkjkjkjkaa"
 let strObj = str.split("").reduce((obj,cur,index,self)=>{
       obj[cur]?obj[cur]++:obj[cur]=1
       return obj
 },{})
 console.log(strObj)