从1d数组创建2d数组

Question

我是编程新手，我有一个任务要求从1d数组创建一个2d数组。我想到了这个(没有任何外部来源的帮助，因为它带走了学习经验(。它适用于我们的教授测试输入，我只是想知道这是一个丑陋/低效的解决方案。

function twoDArray(arr, lenSubArray) {
    var newArr = []; 
    var placeHolder = 0; 
    var leftOver = 0; 
    for (var i = 1; i < arr.length + 1; i++) {
        /* if i is a multiple of the specified sub-array size 
           then add the elements from placeHolder to i
        */
        if (i % lenSubArray === 0) {
            newArr.push(arr.slice(placeHolder, i)); 
            placeHolder += lenSubArray; 
            leftOver++; // tells us how many sub-arrays were created
        }
    }
    /* if original array is not divisible by the length of the specified sub-array
       then there will be left over values. Retrieve these values and create an 
       array out of them and add them to the 2d array.
    */
    if (!(arr.length % lenSubArray === 0)) {
         /* sub-array count multiplied by the length of each 
            sub-array gives us the right index to retrieve remaining values
        */
        leftOver = (leftOver * lenSubArray);
        newArr.push(arr.slice(leftOver))
    }
    return newArr; 
}

测试输入：两个DArray([1，2，3，4，5]，3(输出为：[[1,2,3]，[4,5]]

Answer 1

你太复杂了：

• 创建结果数组
• 将切片从i推送到i+lenSubArray
• i乘以lenSubArray

切片足够智能，可以正确处理阵列的末端

function twoDArray(arr, lenSubArray) {
  var i = 0, result = [];
  while(i < arr.length)
    result.push( arr.slice(i, i+=lenSubArray) );
  return result;  
}

Answer 2

您可以使用Array#reduce并基于索引构建新的数组。

function twoDArray(array, length) {
    return array.reduce(function (r, a, i) {
        i % length ? r[r.length - 1].push(a) : r.push([a]);
        return r;
    }, []);
}
console.log(twoDArray([1, 2, 3, 4, 5], 3));

Answer 3

您不需要对数组进行迭代。您可以使用Array.prototype.slice函数。

function twoDArray(a, b){
    return (Array(Math.ceil(a.length / b)) + '').split(',').map(function(c, d){
        return a.slice(b * d, b * (d + 1));
    });
}

以下是您如何称之为

var a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
console.log(twoDArray(a, 3));
// Output:
// [
//   [1, 2, 3],
//   [4, 5, 6],
//   [7, 8, 9],
//   [10, 11, 12]
// ]