Question

我正在测试一个岩纸剪刀蜥蜴spock游戏。我使用matrix[3,0]来捕捉所有可能性，而不是产生可能的结果。在数组位置console.log(matrix[3,0])，输入的字符串是“摇滚胜利”。但是，我在数组后面运行var matrix = []; matrix[0,0] = "it's a tie"; matrix[0,1] = "Paper wins"; matrix[0,2] = "rock wins"; matrix[0,3] = "rock wins"; matrix[0,4] = "Spock wins"; matrix[1,0] = "Paper wins"; matrix[1,1] = "it's a tie"; matrix[1,2] = "Scissors win"; matrix[1,3] = "Lizard wins"; matrix[1,4] = "Paper wins"; matrix[2,0] = "rock wins"; matrix[2,1] = "Scissors win"; matrix[2,2] = "it's a tie"; matrix[2,3] = "Scissors win"; matrix[2,4] = "spock wins"; matrix[3,0] = "rock wins"; log.console(matrix[3,0]); //returns spock wins并产生了不同的结果。

有人可以告诉我为什么会这样吗？

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Answer 1

不，它没有。它实际上回归“摇滚胜利” 简而言之，您使用的语法不正确。

为什么会这样？

您可能会错过这一部分并直接进入“它应该如何？”如果你对理解JavaScript的神奇行为不感兴趣。

您已声明 1维数组。
当您尝试分配或阅读以下属性matrix[0,0]时，0,0被识别为作为表达式，其被计算为最后一个数字（在本例中为0）。

这意味着

matrix[0,0] = "it's a tie";
matrix[0,1] = "Paper wins";
matrix[0,2] = "rock wins";
// ...
matrix[2,3] = "Scissors win";
matrix[2,4] = "spock wins";
matrix[3,0] = "rock wins";
console.log(matrix[3,0]);

与

matrix[0] = "it's a tie";
matrix[1] = "Paper wins";
matrix[2] = "rock wins";
// ...
matrix[3] = "Scissors win";
matrix[4] = "spock wins";
matrix[0] = "rock wins";
console.log(matrix[0]); // returns "rock wins"

详细了解in this StackOverflow topic。

原因是你使用了错误的语法。

应该怎么做？

这就是你在JavaScript中访问多维数组中的值的方法：

var val = arr[key1][key2][key3]; // not arr[key1, key2, key3]

这就是你的代码应该是这样的：

var matrix = [];
for (var i = 0; i < 4; i++) matrix[i] = [];

matrix[0][0] = "it's a tie";
matrix[0][1] = "Paper wins";
matrix[0][2] = "rock wins";
// ...
matrix[2][3] = "Scissors win";
matrix[2][4] = "spock wins";
matrix[3][0] = "rock wins";
document.write(matrix[3][0]);  // not matrix[3,0]

另一个好的选择是以这种方式描述您的2D阵列：

var matrix = [
    ["it's a tie", "Paper wins", "rock wins"],
    ["Paper wins", "it's a tie", "Scissors wins"]
    // ...     
];

Answer 2

在您的代码中：

matrix[0,0] = "it's a tie";

方括号中的部分是一个被评估并强制转换为字符串的表达式。表达式0,0返回最后一个＆＃34;，＆＃34;之后的值。并且评估为0，0,1评估为1，依此类推。

所以：

var matrix = [];

matrix[0,0] = "it's a tie";
matrix[0,1] = "Paper wins";
matrix[0,2] = "rock wins";
matrix[0,3] = "rock wins";
matrix[0,4] = "Spock wins";
matrix[1,0] = "Paper wins";
matrix[1,1] = "it's a tie";
matrix[1,2] = "Scissors win";
matrix[1,3] = "Lizard wins";
matrix[1,4] = "Paper wins";
matrix[2,0] = "rock wins";
matrix[2,1] = "Scissors win";
matrix[2,2] = "it's a tie";
matrix[2,3] = "Scissors win";
matrix[2,4] = "spock wins";
matrix[3,0] = "rock wins";

创建＆＃34;一维＆＃34;分配给每个索引的最后一个值的数组：

["rock wins", "Scissors win", "it's a tie", "Scissors win", "spock wins"]

和

matrix[3,0]

评估为

matrix[0]

因此你获得了摇滚胜利＆＃34;。

你想要的是：

var matrix = [[],[],[],[]];

matrix[0][0] = "it's a tie";
matrix[0][1] = "Paper wins";
matrix[0][2] = "rock wins";
matrix[0][3] = "rock wins";
matrix[0][4] = "Spock wins";
matrix[1][0] = "Paper wins";
matrix[1][1] = "it's a tie";
matrix[1][2] = "Scissors win";
matrix[1][3] = "Lizard wins";
matrix[1][4] = "Paper wins";
matrix[2][0] = "rock wins";
matrix[2][1] = "Scissors win";
matrix[2][2] = "it's a tie";
matrix[2][3] = "Scissors win";
matrix[2][4] = "spock wins";
matrix[3][0] = "rock wins";

console.log(matrix[3][0]); // rock wins

您还可以使用数组文字：

var matrix = [
              ["it's a tie","Paper wins","rock wins","rock wins","Spock wins"],
              ["Paper wins","it's a tie","Scissors win","Lizard wins","Paper wins"],
              ["rock wins","Scissors win","it's a tie","Scissors win","spock wins"],
              ["rock wins"]
             ];

javascript 2维数组不返回正确的值

2 个答案:

为什么会这样？

应该怎么做？