JavaScript 正则表达式的正面回顾
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Positive look behind in JavaScript regular expression
提问by Raj
I've a document from which I need to extract some data. Document contain strings like these
我有一个文档，我需要从中提取一些数据。文档包含这样的字符串
Text:"How secure is my information?"
I need to extract text which is in double quotes after the literal Text:
我需要提取文字后双引号中的文本 Text:
How secure is my information?
How do I do this with regex in Javascript
如何在 Javascript 中使用正则表达式执行此操作
回答by Andy E
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.
Lookbehind 断言最近已针对 JavaScript 完成，并将出现在 ECMA-262 规范的下一次发布中。它们在 Chrome 66 (Opera 53) 中受支持，但在撰写本文时还没有其他主要浏览器支持。
var str = 'Text:"How secure is my information?"',
reg = /(?<=Text:")[^"]+(?=")/;
str.match(reg)[0];
// -> How secure is my information?
Older browsers do not support lookbehind in JavaScript regular expression. You have to use capturing parenthesis for expressions like this one instead:
较旧的浏览器不支持 JavaScript 正则表达式中的后视。您必须使用捕获括号来代替这样的表达式：
var str = 'Text:"How secure is my information?"',
reg = /Text:"([^"]+)"/;
str.match(reg)[1];
// -> How secure is my information?
This will not cover all the lookbehind assertion use cases, however.
然而，这不会涵盖所有的后视断言用例。
回答by Eddy
I just want to add something: JavaScript doesn'tsupport lookbehinds like (?<= )or (?<! ).
我只想补充一点：JavaScript不支持像(?<= )或(?<! ).
But it doessupport lookaheads like (?= )or (?! ).
但它确实支持像(?= )or那样的前瞻(?! )。
回答by codaddict
You can just do:
你可以这样做：
/Text:"(.*?)"/
Explanation:
解释：
Text:": To be matched literally.*?: To match anything in non-greedy way(): To capture the match": To match a literal"/ /: delimiters
Text:": 字面上匹配.*?: 以非贪婪的方式匹配任何东西(): 捕捉比赛": 匹配文字"/ /: 分隔符
回答by Sjoerd
<script type="text/javascript">
var str = 'Text:"How secure is my information?"';
var obj = eval('({'+str+'})')
console.log(obj.Text);
</script>
回答by Crayon Violent
string.match(/Text:"([^"]*)"/g)
回答by Bill Criswell
If you want to avoid the regular expression all together you can do:
如果你想避免使用正则表达式，你可以这样做：
var texts = file.split('Text:"').slice(1).map(function (text) {
return text.slice(0, text.lastIndexOf('"'));
});
回答by Piotr Berebecki
Here is an example showing how you can approach this.
这是一个示例，展示了如何处理此问题。
1) Given this input string:
1) 给定这个输入字符串：
const inputText =
`Text:"How secure is my information?"someRandomTextHere
Voice:"Not very much"
Text:"How to improve this?"
Voice:"Don't use '123456' for your password"
Text:"OK just like in the "Hackers" movie."`;
2) Extract data in double quotes after the literal Text:so that the results is an array with all matches like so:
2) 在文字后提取双引号中的数据，Text:以便结果是一个包含所有匹配项的数组，如下所示：
["How secure is my information?",
"How to improve this?",
"OK just like in the \"Hackers\" movie."]
SOLUTION
解决方案
function getText(text) {
return text
.match(/Text:".*"/g)
.map(item => item.match(/^Text:"(.*)"/)[1]);
}
console.log(JSON.stringify( getText(inputText) ));
RUN SNIPPET TO SEE A WORKING DEMO
运行片段以查看工作演示
const inputText =
`Text:"How secure is my information?"someRandomTextHere
Voice:"Not very much"
Text:"How to improve this?"
Voice:"Don't use '123456' for your password"
Text:"OK just like in the "Hackers" movie."`;
function getText(text) {
return text
.match(/Text:".*"/g)
.map(item => item.match(/^Text:"(.*)"/)[1]);
}
console.log(JSON.stringify( getText(inputText) ));