CODEWITHSUNDEEP
javascriptregexfirefoxregex-lookarounds
webedward
webedward

Reputation: 103

JS Regex lookbehind not working in firefox and safari

I have this following regex which is working in chrome but causes an error in firefox or safari. I need to modify it to make it work. Can anybody help out a poor soul? Thanks in advance!

regex: /(?=<tag>)(.*?)(?<=<\/tag>)/

Basically, I have to match any char in between <tag> and </tag> and need to retain both tags. I used this expression as an argument to array.split.

input: "The quick brown <tag>fox</tag> jumps over the lazy <tag>dog</tag>"

operation: input.split(regex)

output: ["The quick brown ", "<tag>fox</tag>", " jumps over the lazy ", "<tag>dog</tag>"]

Upvotes: 10

Views: 17342

Answers (2)

Code Maniac
Code Maniac

Reputation: 37755

Firefox and Has
Safari doesn't have support for lookbehind yet, you can use capture group ( used so that this the pattern on which we are splitting will be also be added in output ) and split on <tag> </tag>

let str = "The quick brown <tag>fox</tag> jumps over the lazy <tag>dog</tag>"

let regex = /(<tag>.*?<\/tag>)/

console.log(str.split(regex).filter(Boolean))

Upvotes: 12

Emma
Emma

Reputation: 27723

Maybe, 

<tag>.*?<\/tag>|[^<>]+

would work OK:

Test

function regularExpression(regex, str) {
	let m, arr = [];
	while ((m = regex.exec(str)) !== null) {
		// This is necessary to avoid infinite loops with zero-width matches
		if (m.index === regex.lastIndex) {
			regex.lastIndex++;
		}


		m.forEach((match, groupIndex) => {
			arr.push(match.trim());
			console.log(`Found match, group ${groupIndex}: ${match}`);
		});
	}
	return arr;
}

const expression = /<tag>.*?<\/tag>|[^<>]+/g;
const string = 'The quick brown <tag>fox</tag> jumps over the lazy <tag>dog</tag>';

console.log(regularExpression(expression, string));

If you wish to simplify/modify/explore the expression, it's been explained on the top right panel of regex101.com. If you'd like, you can also watch in this link, how it would match against some sample inputs.

RegEx Circuit

jex.im visualizes regular expressions:

enter image description here

Upvotes: 1

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