找出某个值在给定数组中的位置

var arr = [20,10,33, 14, 16];
var item = 16;
function choose(arr, item){
    for(var i = 0; i < arr.length; i++){
        if(arr[i] == item) return i;
    }
    return -1;
}

var end = choose(arr, item);
console.log(end);

var arr = [20,10,33,14, 16];
var item = 13;

var arr = [20,10,33,14, 16];
var item = 13;

function choose(arr, item){
    var back = -1;
    var i = 0;
    arr.reduce((newarr, one)=>{
        if(one == item){
            back = i;
        }
        i = i + 1;
    },[]);
    return back;
}

var end = choose(arr, item);
console.log(end);


var arr = [20,10,33,14, 16];
var item = 16;

function indexOf(arr, item){
    return arr.indexOf(item);
}
var end = indexOf(arr, item);
console.log(end);

var arr = [20,10,33,14, 16];
var item = 16;

function choose(arr, item){
    if(Array.prototype.indexOf){
        return arr.indexOf(item);
    }
    else{
        for(var i = 0; i < arr.length; i++){
            if(arr[i] == item) return i;
        }
        return -1;
    }
}

var end = choose(arr, item);
console.log(end);