Question

嘿伙计们，我需要帮助，请：P

此代码有什么问题？

var arr = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
var narr = []; // want to be like that [[1, 4, 7], [2, 5, 8], [3, 6, 9]]

function arange(mass) {
    for (var i = 0; i < mass.length; i++) {
        for (var j = 0; j < mass[i].length; j++) {
            narr[mass[i]].push(mass[j][i]);
        }
    }
}

如果我调用该函数有一个问题：＆＃34; TypeError：无法读取属性＆＃39; push＆＃39;未定义的。＆＃34;谢谢。另外link here

Answer 1

您不小心尝试在值push上调用narr而不是数组本身。当然，原始值没有定义push函数。您的代码应如下所示：

var mass = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
var narr = [];

function arange(mass) {
    for (var i = 0; i < mass.length; i++) {
        var innerArray = [];
        for (var j = 0; j < mass[i].length; j++) {
            innerArray.push(mass[j][i]);
        }
        narr.push(innerArray);
    }
}

Answer 2

只需选择正确的元素来分配值。

var arr = [
        [1, 2, 3],
        [4, 5, 6],
        [7, 8, 9]
    ];

function arange(mass) {
    var narr = [];
    for (var i = 0; i < mass.length; i++) {
        for (var j = 0; j < mass[i].length; j++) {
            narr[j] = narr[j] || [];
            narr[j][i] = mass[i][j];
        }
    }
    return narr;
}

document.write('<pre>' + JSON.stringify(arange(arr), 0, 4) + '</pre>');

ES6

var arr = [
        [1, 2, 3],
        [4, 5, 6],
        [7, 8, 9]
    ];

function arange(mass) {
    var narr = [];
    mass.forEach((a, i) => a.forEach((b, j) => {
        narr[j] = narr[j] || [];
        narr[j][i] = mass[i][j];
    }));
    return narr;
}

document.write('<pre>' + JSON.stringify(arange(arr), 0, 4) + '</pre>');

Answer 3

您需要添加一个临时数组来存储中间值：

var arr = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ];

var narr = []; 

function arange(mass) {
    for (var i = 0; i < mass.length; i++) {
        var t = []; // temporary array
        for (var j = 0; j < mass[i].length; j++) {
            t.push(mass[j][i]);
        }
        narr.push(t);
    }
}

arange(arr);

document.write(JSON.stringify(narr));

Answer 4

或者你可以使用这个ES6一个班轮

＆＃13;

var arr = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ];
    
var res = arr.map((e, i) => e.map((_, j) => arr[j][i]));

document.write(JSON.stringify(res));

＆＃13;

多维数组JAVASCRIPT出错了

4 个答案: