为什么拼接方法有这种奇怪的行为？ [英] Why does the splice method have this strange behavior?

问题描述

在我的应用程序需要从一个数组中删除的元素。不过，我是新来的JS。我在网上搜索，每一个博客文章在谈论拼接（）方法。所以，我认为用它，但它有一个很奇怪的行为。

In my application I need to delete an element from an array. However I am new to JS. I searched the web and every blog post was talking about splice() method. So I considered to used it, but it has a very strange behavior.

在这里，我找到了帖子：
http://www.w3schools.com/jsref/jsref_splice.asp
http://viralpatel.net/blogs/javascript-array-remove-element-js-array-delete-element/

Here the post I found : http://www.w3schools.com/jsref/jsref_splice.asp http://viralpatel.net/blogs/javascript-array-remove-element-js-array-delete-element/

下面是我的测试：

it("should delete all elements in array", function () {
    var ary = new Array();

    for (i = 0; i < 10; i++) {
        ary[i] = Math.random();
    }

    expect(ary.length).toBe(10);

    for (i = 0; i < 10; i++) {
        ary.splice(i, 1);
    }

    expect(ary.length).toBe(0);

});

这里是测试结果：

And here is the result of the test:

  Firefox 15.0.1 Linux: Run 7 tests (Passed: 6; Fails: 1; Errors 0) (44.00 ms)
    should delete all elements in array failed (5.00 ms): Error: Expected 5 to be 0.

我用角JS。

非常感谢您的答复。这里是另一个试验，只是不通过：

Thanks very much for replies. Here is another test that just don't pass:

var ary = new Array();

        ary = ['a', 'b', 'c', 'd'];

        ary.splice(0, 1);

        ary.splice(1, 1);

        ary.splice(2, 1);

        ary.splice(3, 1);

        expect(ary.length).toBe(0);

Firefox 15.0.1 Linux: Run 7 tests (Passed: 6; Fails: 1; Errors 0) (49.00 ms)
    Posting server policy.should delete all elements in array failed (5.00 ms): Error: Expected 2 to be 0.

作为@Matteo Tassinari认为这应该应该删除右边的所有元素？

as @Matteo Tassinari suggest this should one should delete all elements right ??

推荐答案

原因很简单：每一个新的拼接您的阵列将变得更短：

The reason is simple: with each new splice your array will become shorter:

var arr = [1, 2, 3];
arr.splice(0, 1);
console.log(arr[0]); // 2
console.log(arr[2]); // undefined
console.log(arr.length); // 2

在您的code的第二个循环拼接将改变你的数组只有五次。但是，第六次（当 I 将等于5）， arr.splice（5,1）操作有效地导致无操作，因为你的阵列将是已经5个元素而已。

In the second loop of your code splice will change your array only five times. But the sixth time (when i will be equal to 5), arr.splice(5, 1) operation will effectively result in no-op, as your array will be already of 5 elements only.

您可以修复它​​作为@MatteoTassinari答案，或者只是使用拼接（0，1）（或只是移（））代替拼接（I，1）。

You can fix it as in @MatteoTassinari answer, or just use splice(0, 1) (or just shift()) instead of splice(i, 1).

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