手写数组.property.map

前端理解数组map方法functionmap(arr,callBack){//先判断arr是否为数组，callBack是否为函数，如果不是，直接返回空数组if(!Array.isArray(arr)||!arr.length||typeofcallBack!='function')return[]else{varresult=[]//遍历数组arrfor(leti=0,len=arr.length;i{console.log(项目)console.log(index)console.log(arr)console.log(item*2)returnitem*10})//9//0//[9,8,5]//18////8//1//[9,8,5]//16////5//2//[9,8,5]//10////[90,80,50]//数组映射用例arr985.map((item,index,arr)=>{console.log(item)console.log(index)console.log(arr)console.log(item*2)returnitem*10;})//9//0//[9,8,5]//18////8//1//[9,8,5]//16////5//2//[9,8,5]//10////[90,80,50]