我有一个javascript代码如下。
var row = new Array(7);
row.fill(0);
var state = new Array(7);
state.fill(row);
state[0][3] = 2;
console.log(state);
我的问题是，当我更改一个元素state[0][3] = 2;时，它会影响所有行。所有行的第3个索引值变为2.有人可以告诉这段代码有什么问题吗？
答案 0 :(得分：3)
有人能说出这段代码有什么问题吗？
您在<{1}}中使用一个 row数组来所有您的条目。 state获取您提供的值并将该值重复放入目标数组中。您提供的价值是对您创建的单个数组的引用，因此所有条目最终都会引用相同的行，像这样：
+−−−−−−−−−+
row−−−−−−−−−−−−−−−−−−−−−−−+−+−+−+−+−+−+−−>| (array) |
+−−−−−−−−−+ | | | | | | | +−−−−−−−−−+
state−−−−>| (array) | | | | | | | | | 0: 0 |
+−−−−−−−−−+ | | | | | | | | 1: 0 |
| 0 |−−−−−+ | | | | | | | 2: 0 |
| 1 |−−−−−−−+ | | | | | | 3: 0 |
| 2 |−−−−−−−−−+ | | | | | 4: 0 |
| 3 |−−−−−−−−−−−+ | | | | 5: 0 |
| 4 |−−−−−−−−−−−−−+ | | | 6: 0 |
| 5 |−−−−−−−−−−−−−−−+ | +−−−−−−−−−+
| 6 |−−−−−−−−−−−−−−−−−+
+−−−−−−−−−+
您需要为fill中的每个广告位创建一个新的行数组：
statelet state = Array.from({length:7}, () => {
return new Array(7).fill(0);
});
state[0][3] = 2;
console.log(state);
...或仅包含ES5中的功能：
.as-console-wrapper {
max-height: 100% !important;
}var state = [0,0,0,0,0,0,0].map(function() {
return [0,0,0,0,0,0,0];
});
state[0][3] = 2;
console.log(state);