Why does the statement if ( !condition ) { console.log(condition) } display true
javascript, regex
Solution
This is due to a bug in Javascript RegEx engine (ECMAScript3)
Basically a regex with the `g` modifier doesn't reset correctly, so multiple `test()` calls toggle between `true and false`.
- See also this answer: https://stackoverflow.com/a/3827500/548225 for more details.
Problem
I want to make a String method, which accepts a RegExp and a callback, then splits String by RegExp, and inserts callback's return in split array. In short, it would do something like this: ``` "a 1 b 2 c".method(/\d/, function ($1) { return $1 + 1; }) => [a, 2, b, 3, c] ``` In case the String doesn't match the RegExp, it should return an array, like this: ``` "a b c d e".method(/\d/, function ($1) { return $1 + 1; }) => ["a b c d e"] ``` I wrote this code, but it doesn't work as I thought: ``` String.prototype.preserveSplitReg = function(reg, func) { var rtn = [], that = this.toString(); if (!reg.test(that)) { console.log(reg, that, reg.test(that)); return [that]; } ... } ``` The console.log should be called ONLY when the String doesn't match `reg`, right? But sometimes it logs `(reg, that, true)`. That troublesome String and `reg` were: ``` "See <url>http://www.w3.org/TR/html5-diff/</url> for changed elements and attributes, as well as obsolete elements and" /<url>.*?<\/url>/g ``` console logs true. I can't figure out why. Any help would be highly appreciated.