Regex - check if input still has chances to become matching

Question

We\'ve got such regexp:

var regexp = /^one (two)+ three/;

So only string like \"one two three\" or \"one two three four\

Answer 1

That's actually quite an interesting question.

Personally, I'd do it with the RegExp constructor, so the query can be broken down:

var input = "one ";
var query = "^one two three";
var q_len = query.length;
var match;
for( var i=1; i<=q_len; i++) {
    match = input.match(new RegExp(query.substr(0,i));
    if( !match) {alert("Pattern does NOT match"); break;}
    if( match[0].length == input.length) {alert("Input is promising!"); break;}
    // else continue to the next iteration
}

Obviously you can handle the "exact match" case up front to avoid the whole loop thing. If the whole pattern matches the input, then you're all good.

EDIT: I've just realised that this will not work for groups and stuff. It will fail on account of malformed regexes, but I hope it can serve as a basis for your query.