查找字符串中指定字符的所有索引 [英] Finding all indexes of a specified character within a string

问题描述

例如，如果我在变量中有剪刀，并想知道所有出现的字母的位置s，它应该打印出来 1,4,5,8

For example if I had "scissors" in variable and wanted to know the position of all occurrences of the letter "s", it should print out 1, 4, 5, 8

我该如何做到这一点JavaScript以最有效的方式？我不认为循环整体是非常有效的

How can I do this in JavaScript in most efficient way? I don't think looping through the whole is terribly efficient

推荐答案

一个简单的循环效果很好：

A simple loop works well:

var str = "scissors";
var indices = [];
for(var i=0; i<str.length;i++) {
    if (str[i] === "s") indices.push(i);
}

现在，您表明您想要1,4,5,8。这将给你0,3,4,7，因为索引是从零开始的。所以你可以添加一个：

Now, you indicate that you want 1,4,5,8. This will give you 0, 3, 4, 7 since indexes are zero-based. So you could add one:

if (str[i] === "s") indices.push(i+1);

现在它会给你预期的结果。

and now it will give you your expected result.

小提琴可以在这里看到。

我不认为循环整体是非常有效的

I don't think looping through the whole is terribly efficient

就性能而言，在你开始遇到问题之前，我不认为这是你需要非常担心的事情。

As far as performance goes, I don't think this is something that you need to be gravely worried about until you start hitting problems.

这是一个 jsPerf 测试比较各种答案。在Safari 5.1中，IndexOf表现最佳。在Chrome 19中，for循环是最快的。

Here is a jsPerf test comparing various answers. In Safari 5.1, the IndexOf performs the best. In Chrome 19, the for loop is the fastest.

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