function findAllOccurrences(arr, target) { //在数组 arr 中,查找值与 item 相等的元素出现的所有位置 /*for...in +push*/ let a=[]; for(let i in arr){ if(arr[i]==target){ a.push(i); } } return a; /*filter()方法*/ let res=[]; arr.filter((item,index)=>{ return item===target&&res.push(index); }); return res; //indexOf(searchValue[,start]): let res=[]; let index=arr.indexOf(target); while(index!=-1){ res.push(index); index=arr.indexOf(target,index+1); } return res; }
function findAllOccurrences(arr, target) { var arr2 = [] arr.forEach((el,index,arr)=>{ if(el === target){ arr2.push(index) } }) return [...new Set(arr2)] }
function findAllOccurrences(arr, target) { //for var newArr=[] for(let i =0 ;i<arr.length;i++){ if(arr[i]==target){ newArr.push(i) } } return newArr; //indexOf var temp=arr.indexOf(target); var newArr=[]; while(temp>-1){ newArr.push(temp); temp=arr.indexOf(target,temp+1); } return newArr; //fliter var newArr=[]; arr.filter(function(item,index){ return item===target&&newArr.push(index); }); return newArr; }