我很难弄清楚如何移动数组中的一个元素。例如,给定以下条件:

var array = [ 'a', 'b', 'c', 'd', 'e'];

我怎么能写一个函数来移动元素'd'到'b'的左边?

还是c右边的a ?

移动元素之后,应该更新其余元素的索引。结果数组将是:

array = ['a', 'd', 'b', 'c', 'e']

这看起来应该很简单,但我无法理解它。


当前回答

我喜欢不可变的,函数式的语句:)…

const swapIndex = (array, from, to) => (
  from < to 
    ? [...array.slice(0, from), ...array.slice(from + 1, to + 1), array[from], ...array.slice(to + 1)] 
    : [...array.slice(0, to), array[from], ...array.slice(to, from), ...array.slice(from + 1)]
);

其他回答

您可以实现一些基本的演算,并创建一个通用函数来将数组元素从一个位置移动到另一个位置。

对于JavaScript,它看起来是这样的:

function magicFunction (targetArray, indexFrom, indexTo) { 

    targetElement = targetArray[indexFrom]; 
    magicIncrement = (indexTo - indexFrom) / Math.abs (indexTo - indexFrom); 

    for (Element = indexFrom; Element != indexTo; Element += magicIncrement){ 
        targetArray[Element] = targetArray[Element + magicIncrement]; 
    } 

    targetArray[indexTo] = targetElement; 

}

查看“移动数组元素”在“忧郁”的详细解释。

https://web.archive.org/web/20121105042534/http://www.gloommatter.com:80/DDesign/programming/moving-any-array-elements-universal-function.html

splice()方法的作用是:向数组中添加/从数组中删除项,并返回已删除的项。 注意:该方法会改变原始数组。/ w3schools /

Array.prototype.move = function(from,to){
  this.splice(to,0,this.splice(from,1)[0]);
  return this;
};

var arr = [ 'a', 'b', 'c', 'd', 'e'];
arr.move(3,1);//["a", "d", "b", "c", "e"]


var arr = [ 'a', 'b', 'c', 'd', 'e'];
arr.move(0,2);//["b", "c", "a", "d", "e"]

由于函数是可链的,这也工作:

alert(arr.move(0,2).join(','));

演示

var ELEMS = ['a', 'b', 'c', 'd', 'e']; /* Source item will remove and it will be placed just after destination */ function moveItemTo(sourceItem, destItem, elements) { var sourceIndex = elements.indexOf(sourceItem); var destIndex = elements.indexOf(destItem); if (sourceIndex >= -1 && destIndex > -1) { elements.splice(destIndex, 0, elements.splice(sourceIndex, 1)[0]); } return elements; } console.log('Init: ', ELEMS); var result = moveItemTo('a', 'c', ELEMS); console.log('BeforeAfter: ', result);

不复制数组的不可变版本:

const moveInArray = (arr, fromIndex, toIndex) => {
  if (toIndex === fromIndex || toIndex >= arr.length) return arr;

  const toMove = arr[fromIndex];
  const movedForward = fromIndex < toIndex;

  return arr.reduce((res, next, index) => {
    if (index === fromIndex) return res;
    if (index === toIndex) return res.concat(
      movedForward ? [next, toMove] : [toMove, next]
    );

    return res.concat(next);
  }, []);
};

我喜欢不可变的,函数式的语句:)…

const swapIndex = (array, from, to) => (
  from < to 
    ? [...array.slice(0, from), ...array.slice(from + 1, to + 1), array[from], ...array.slice(to + 1)] 
    : [...array.slice(0, to), array[from], ...array.slice(to, from), ...array.slice(from + 1)]
);