Regex / lastIndex - 意外行为 [英] Regex/lastIndex - Unexpected behaviour

问题描述

我知道有一些正则表达式/ lastIndex 差异，但这个对我来说是新的！

I know there are a few regex/lastIndex discrepancies but this one is new to me!

预期行为：显然，创建一个新的正则表达式（带有文字/构造函数）将创建一个带有 lastIndex的新RegExp对象 属性设置为零。

Expected behaviour: Creating a new regular expression (with literal/constructor) will, obviously, create a new RegExp object with a lastIndex property set to zero.

实际行为 :(在FF，Chrome中）：lastIndex属性似乎坚持多个RegExp创作。

Actual behaviour: (in FF, Chrome): The lastIndex property seems to persist through multiple RegExp creations.

例如

function foo(s) {

    // A *NEW* regular expression
    // is created on each call of foo():
    var regex = /ABC/g;

    document.write( regex.lastIndex + '<br/>' );

    // regex.test() updates lastIndex property
    regex.test(s);

    // This is where the regex's life should end...
    // (Why does it persist?)

}

foo('ABC');
foo('ABCABC');
foo('ABCABCABC');

见这里： http://jsbin.com/otoze

See here: http://jsbin.com/otoze

正在为每个函数调用创建一个新的RegExp对象（对吗？），为什么以下内容被写入文档？ -

A new RegExp object is being created on every function call (right?), so why is the following being written to the document?? -

0
3
6

???

注意，这种奇怪现象似乎发生在FF（3）和Chrome（2）中但是，奇怪的是不是IE。

Note, this weirdness appears to happen in FF(3) and Chrome(2), but, curiously not IE.

这是预期的行为，IE是错误的还是对的？这是一个众所周知的错误吗？

Is this expected behaviour, does IE get it wrong or right? Is this a well-known bug?

编辑：当使用构造函数实例化正则表达式时，这似乎不会发生而不是文字。例如。 新的RegExp（'ABC'，'g'）; ......但是，文字应该（理论上）正常工作，对吗？

this doesn't appear to happen when instantiating the regex with a constructor instead of a literal. E.g. new RegExp('ABC','g'); ... Still, the literal should (theoretically) work, right?

推荐答案

var regex = new RegExp（ABC，g）; 没有那个问题，所以我猜 / ABC / g 重新使用正则表达式对象。

var regex = new RegExp("ABC", "g"); doesn't have that problem, so I guess /ABC/g re-uses regexp objects.

编辑：显然这是根据ECMAScript 3.0规范的正确行为，它已在ECMAScript 3.1中修复 - 详情

Apparently this is correct behavior according to the ECMAScript 3.0 specification, it's fixed in ECMAScript 3.1 - details

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