Question

我有一个数组

var itemsArr = ["blue", "wine", "orange", "yellow", "cyan"];

如何从数组的END到FRONT获取一定数量的数组元素？

预期产出：

示例1：

//shift final 3 elements
var expected = ["orange", "yellow", "cyan", "blue", "wine"];

示例2：

//shift final 2 elements
var expected = ["yellow", "cyan", "blue", "wine", "orange"];

Answer 1

这是一种方法：

JSBin Example

var a = ["blue", "wine", "orange", "yellow", "cyan"];

function shifter(arr, n) {
  var shifted = arr.splice(-n);
  return shifted.concat(arr);
}


console.log(shifter(a, 3));

Answer 2

您可以与Array#splice和Array#concat结合使用。

var itemsArr = ["blue", "wine", "orange", "yellow", "cyan"];

itemsArr = itemsArr.splice(-3).concat(itemsArr);
document.write('<pre>' + JSON.stringify(itemsArr, 0, 4) + '</pre>');

itemsArr = itemsArr.splice(3).concat(itemsArr);
document.write('<pre>' + JSON.stringify(itemsArr, 0, 4) + '</pre>');

Answer 3

function moveToFront(x, noFromEnd){
    if(noFromEnd > x.length){
        alert("Immpossible");
    }
    else if(noFromEnd == x.length){
        return x;
    }
    else if(noFromEnd < 0){
        alert("immpossible")
    }
    else if(noFromEnd == 0){
        return x;
    }
    else{
        var returnArray = []
        for(var i=(x.length-noFromEnd);i<x.length;i++){
            returnArray.push(x[i])
        }
        for(var i=0; i<(x.length-noFromEnd); i++){
            returnArray.push(x[i])
        }
        return returnArray;
    }
}

将最终给定的elemts数移到数组前

3 个答案: