CODEWITHSUNDEEP
javascriptregexlookbehind
androidkc
androidkc

Reputation: 709

How do I convert a PHP regex with a lookbehind to Javascript?

Javascript doesn't support lookbehinds in regexes. How do I convert the following PHP regex to Javascript?

regPattern="(?<!\\)\\x"

Here is the test case (in Node.js):

var str = '{"key":"abc \\x123 \xe2\x80\x93 xyz"}'
var newStr = str.replace(/regPattern/g, '\\u')
console.log(newStr); // output: '{"key":"abc \\x123 \ue2\u80\u93 xyz"}'

\\x123 doesn't match because it contains \\x, but \x matches.

Upvotes: 0

Views: 165

Answers (1)

KernelPanic
KernelPanic

Reputation: 600

Try this:

var newStr = str.replace(/([^\\]|^)\\x/g, '$1\\u');

In other words, match the ^ (start of string) or any non-\ character, followed by \x, capturing the first character in capture group 1.

Then replace the whole 3-character matched group with capture group 1, followed by \u.

For example, in abc?\x, the string ?\x will be matched, and capture group 1 will be ?. So we replace the match (?\x) with $1\u, which evaluates to ?\u. So abc?\x -> abc?\u.

Upvotes: 1

Related Questions