CODEWITHSUNDEEP
javascriptjqueryregexstring
faressoft
faressoft

Reputation: 19641

How to extract a text using regex?

What is the problem with my code

var str = "[356] Hello World";
var patt = new RegExp("(?!\[)\d+(?<!\])","");
var result = patt.exec(str);

Result Should Be = 356

Upvotes: 2

Views: 168

Answers (3)

Justin Morgan
Justin Morgan

Reputation: 30695

In addition to what others have pointed out, you have the wrong syntax for lookarounds.

  • (?!regex) is a negative lookahead, but you're using it as a positive lookbehind.
  • (?<!regex) is a negative lookbehind, but you're using it as a positive lookahead.

Since lookbehinds aren't supported in JS, Thai's and lonesomeday's answers are the way to go. In a language that did support them, you'd want this:

/(?<=\[)\d+(?=\])/

Upvotes: 1

Thai
Thai

Reputation: 11354

Lookbehinds are not supported in JavaScript.

You can instead try using capturing subpatterns.

var str = "[356] Hello World";
var match = str.match(/\[(\d+)\]/);
var result = match ? match[1] : null;

Upvotes: 1

lonesomeday
lonesomeday

Reputation: 237817

The problem is that you can't do negative lookbehinds in Javascript.

Something like this should work:

var str = '[356] Hello World',
    patt = /\[(\d+)\]/,
    result = patt.exec(str)[1];

This creates a matching group and selects the match with [1].

Upvotes: 2

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