javascript - 在 JavaScript 中递增多维数组

Question

我目前正在做一些非常基础的事情，但我遇到了困难。我想在二维数组中获取一个随机索引，并在每次 for 循环翻转时将其递增 1。

var dice = [[],[]];

// Get totals.
for(var i = 0; i < 30000; i++) {
    var dieOne = Math.floor(Math.random() * 6 + 1);
    var dieTwo = Math.floor(Math.random() * 6 + 1);
        dice[[dieOne][dieTwo]]++;
    }

    // All index values equal 30,000 for some reason
    alert(dice[[1][3]]);

为什么这个 for 循环会将所有索引设置为 30,000？我是否错误地使用了 JavaScript 数组？

谢谢。

Answer 1

你在做什么

您似乎误解了您正在做的事情的语法。目前相当于

var dieOne = Math.floor(Math.random() * 6 + 1);
var dieTwo = Math.floor(Math.random() * 6 + 1);
var foo;
foo = dieOne; // a number
foo = [foo];  // an array with one number in it
foo = foo[dieTwo]; // probably undefined, unlikely case of `dieTwo = 0`
                   // which would give back `dieOne`
dice[foo] = dice[foo] + 1; // most likely trying to add 1 to property `undefined`

然后你在做

foo = [1]; // an array length 1
foo = foo[3]; // undefined, it doesn't have an item here
foo = dice[foo]; // = dice[undefined] = undefined
alert(foo); // alerting "undefined"

---

你可能想做什么

看起来您实际上想要一个 Array 6 Array 每个 6 Numbers;构建你最喜欢的方式

var dice = [
    [0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0]
];

然后你的循环是

var dieOne, dieTwo, i;
for(i = 0; i < 30000; ++i) {
    dieOne = Math.floor(Math.random() * 6); // indices start at 0 and
    dieTwo = Math.floor(Math.random() * 6); // 6 of them means max is 5
    dice[dieOne][dieTwo]++; // count the brackets here..
}

然后说你想知道有多少次 dieOne = 1, dieTwo = 3，你会看看

dice[1][3]; // count the brackets again.