JavaScript正则表达式背后的正面看法 [英] Positive look behind in JavaScript regular expression

问题描述

我有一份文件，我需要从中提取一些数据。文档包含这些字符串

I've a document from which I need to extract some data. Document contain strings like these

Text:"How secure is my information?"

我需要在文字文本之后提取双引号的文本：

How secure is my information?

如何在Javascript中使用正则表达式执行此操作

How do I do this with regex in Javascript

推荐答案

Lookbehind断言最近已针对JavaScript进行了最终确定，并将出现在ECMA-262规范的下一个出版物中。 Chrome 66（Opera 53）支持它们，但在撰写本文时没有其他主流浏览器。

Lookbehind assertions were recently finalised for JavaScript and will be in the next publication of the ECMA-262 specification. They are supported in Chrome 66 (Opera 53), but no other major browsers at the time of writing.

var str = 'Text:"How secure is my information?"',
    reg = /(?<=Text:")[^"]+(?=")/;

str.match(reg)[0];
// -> How secure is my information?

较旧的浏览器不支持JavaScript正则表达式中的lookbehind。你必须使用捕获括号表示这样的表达式：

Older browsers do not support lookbehind in JavaScript regular expression. You have to use capturing parenthesis for expressions like this one instead:

var str = 'Text:"How secure is my information?"',
    reg = /Text:"([^"]+)"/;

str.match(reg)[1];
// -> How secure is my information?

然而，这并不包括所有看起来断言的用例。

This will not cover all the lookbehind assertion use cases, however.

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