gistfile1.js

// So this will run in a browser as well as a shell.
if (this.window) window.print = function(s) { console.log(s); }

var TOTAL = 1e6;
var str = "color: red";

// Test with regex
(function() {
    var start = Date.now();
    for (var i=0; i<TOTAL; ++i) {
        var match = str.match(/[^:]+/);
        if (match)
            match[0];
    }
    var end = Date.now();
    print(end-start+'ms');
})();

// Test with substring
(function() {
    var start = Date.now();
    for (var i=0; i<TOTAL; ++i) {
        var index = str.indexOf(':');
        if (index >= 0)
            str.substring(0, str.indexOf(':'));
    }
    var end = Date.now();
    print(end-start+'ms');
})();