更改数组中的元素位置,并在其间移动元素

Question

我想在数组中选择一个元素,将其移动到另一个索引,然后将"中间"元素"移位/旋转"1.

想象一下拖放功能,如果索引from小于索引to,那么我想转移到左边,然后转移到右边.

输入:

let data = [ 0, 1, 2, 3, 4, 5, 6 ]

任务1: insertAndShift(data, 0, 3): Take element at index 0, shift indexes 1, 2, 3 to the left, and then insert index 0 at 3

预期产出:

[ 1, 2, 3, 0, 4, 5, 6 ]

TASK2: insertAndShift(data, 3, 0) Take element at index 3, shift indexes 0, 1, 2 to the right and then insert index 3 at 0

预期产出:

[ 0, 1, 2, 3, 4, 5, 6 ]

我试过这个:

下面旋转一个数组,丑陋而不工作的代码(temp总是未定义+结果不完整+可能仅适用于RIGHT):

insertAndShift(data, from, to)
{
    if(from < to)
    {
        // rotate in between - LEFT

    }
    else
    {    
        // swap elements
        let temp = data[from];
        data[from] = data[to];
        data[to] = temp;

        // rotate in between - RIGHT
        let newData = this.rotate(data.slice(to, from - 1), 1)

        let result = [];
        result.push(data.slice(0,1));
        newData.map((element) => result.push(element))
        for(let i = from+1; i < data.length; i++)
        {
            result.push(data[i]);
        }

        this.setState({data: result})
    }
}

rotate(arr, k) {
    var l = arr.length;
    arr = this.reverseArr(arr, 0, l - 1);
    arr = this.reverseArr(arr, 0, k - 1);
    arr = this.reverseArr(arr, k, l - 1);
    return arr;
}

reverseArr(arr, left, right) {
    while (left < right) {
        var temp = arr[left];
        arr[left] = arr[right];
        arr[right] = temp;
        left++;
        right--;
    }
    return arr;
}

也可以按照Javascript(动态)插入到数组中,然后将所有元素移到+1下面,这只返回1个项目:

else
{
    let result = data.splice(to, 1, data[from]);
    this.setState({allTasksArray: result})
}

我怎样才能实现左右两种目的？

Answer 1

您可以使用Array.prototype.splice切出所需的元素并插入所需的索引(移动将自动进行):

function insertAndShift(arr, from, to) {
    let cutOut = arr.splice(from, 1) [0]; // cut the element at index 'from'
    arr.splice(to, 0, cutOut);            // insert it at index 'to'
}



let data = [ 0, 1, 2, 3, 4, 5, 6 ];

insertAndShift(data, 0, 3);
console.log("[" + data + "]");

insertAndShift(data, 3, 0);
console.log("[" + data + "]");