js数组

在数组 arr 中，查找值与 item 相等的元素出现的所有位置

链接：https://www.nowcoder.com/questionTerminal/0a9af9cb20c34babb6232126e019c74d
来源：牛客网

//filter
function findAllOccurrences(arr, target) {
    var result=[];
    arr.filter(function(item,index){
        return item===target&&result.push(index);
    });
    return result;
}
//for
function findAllOccurrences(arr, target) {
    var result=[];
    for(var i=0;i<arr.length;i++){
        if(arr[i]===target){
            result.push(i);
        }
    }
    return result;
}
//lastIndexOf+slice/splice
function findAllOccurrences(arr, target) {
    var result=[],index=arr.lastIndexOf(target);
    while(index>-1){
        result.push(index);
        arr.splice(index,1);//arr=arr.slice(0,index);
        index=arr.lastIndexOf(target);
    }
    return result;
}
//indexOf
function findAllOccurrences(arr, target) {
    var result=[],index=arr.indexOf(target);
    while(index>-1){
        result.push(index);
        index=arr.indexOf(target,index+1);
    }
    return result;
}