Question

我试图在JavaScript中创建一个重新排列数组索引的函数。我提出了以下想法，但是使用这种方法我必须为方法reformatArray的第四个参数提供一个新的if if子句，用于每个可能的数组长度。可以更直观的方式添加方法中的参数吗？

代码：

function start() {
    var array1 = ["Item 1", "Item 2", "Item 3", "Item 4", "Item 5", "Item 6", "Item 7", "Item 8"];

    reformatArray(array1, 1, 2, [1, 2, 0]);
    //output should be ["Item 1", "Item 3", "Item 4", "Item 2", "Item 4", "Item 5", "Item 6", "Item 7", "Item 8"] 
    //WORKS

    var array2 = ["Item 1", "Item 2", "Item 3", "Item 4", "Item 5", "Item 6", "Item 7", "Item 8"];

    reformatArray(array2, 2, 5, [3, 1, 3, 2]);
    //output should be ["Item 1", "Item 2", "Item 6", "Item 4", "Item 6", "Item 5", "Item 8"] 
    //DOES NOT WORK because array as fourth argument is greater than 3 in length
}

function reformatArray(array, startIndex, numOfIndicesToReplace, newIndicesPositions) {
    var newPosLength = newIndicesPositions.length;

    if (newPosLength == 0) {
        array.splice(startIndex, numOfIndicesToReplace);
    } else if (newPosLength == 1) {
        array.splice(startIndex, numOfIndicesToReplace, array[startIndex + newIndicesPositions[0]]);
    } else if (newPosLength == 2) {
        array.splice(startIndex, numOfIndicesToReplace, array[startIndex + newIndicesPositions[0]], array[startIndex + newIndicesPositions[1]]);
    } else if (newPosLength == 3) {
        array.splice(startIndex, numOfIndicesToReplace, array[startIndex + newIndicesPositions[0]], array[startIndex + newIndicesPositions[1]], array[startIndex + newIndicesPositions[2]]);
    }
    //etc.
}

提前致谢。

Answer 1

您可以创建要传递给拼接的参数列表，并使用Function.prototype.apply将它们传递给拼接。

function reformatArray(array, startIndex, numOfIndicesToReplace, newIndicesPositions) {
  var newPosLength = newIndicesPositions.length;
  var params = [startIndex, numOfIndicesToReplace];

  newIndicesPositions.forEach(function(val, pos) {
    params.push(array[startIndex + newIndicesPositions[pos]])
  });

  array.splice.apply(array, params);
}

Answer 2

使用apply。第一个参数是this的约束，第二个是参数数组。

array.splice.apply(null, arrayOfArguments)

Answer 3

将参数作为对象。这有助于扩展参数计数。

function reformatArray(params) {
    var array = params.array;
    var startIndex = params.startIndex;
    var numOfIndicesToReplace = params.numOfIndicesToReplace;
    var newIndicesPositions = params.newIndicesPositions;

    var newPosLength = newIndicesPositions.length;

    if (newPosLength == 0) {
        array.splice(startIndex, numOfIndicesToReplace);
    } else if (newPosLength == 1) {
    array.splice(startIndex, numOfIndicesToReplace, array[startIndex +      newIndicesPositions[0]]);
    } else if (newPosLength == 2) {
        array.splice(startIndex, numOfIndicesToReplace, array[startIndex + newIndicesPositions[0]], array[startIndex + newIndicesPositions[1]]);
    } else if (newPosLength == 3) {
        array.splice(startIndex, numOfIndicesToReplace, array[startIndex + newIndicesPositions[0]], array[startIndex + newIndicesPositions[1]], array[startIndex + newIndicesPositions[2]]);
    }
     //etc.
 }

或者您可以在方法内使用Arguments对象。参数是一个关键字。 arguments对象是一个类似于Array的对象，对应于传递给函数的参数。有关Arguments关键字语法的更多信息，请查看MDN网站。

Answer 4

这是另一种方法，你可以通过拼接数组本身然后连接数组来实现它

function reformatArray2(array, startIndex, numOfIndicesToReplace, newIndicesPositions) {        
    var replaceValues = newIndicesPositions.map(function(index) {
      return array[startIndex + index];
    })

    array.splice(startIndex, numOfIndicesToReplace, replaceValues);
    return [].concat.apply([], array);
}

Plunker Demo

（数组展平技术found here）

更直观的重新排列阵列的方法

4 个答案: