Parsing a string to an object
I believe a simple split on newline and a hard-coded parse would be better than the regex solution.... especially if you can trust your input data will be valid. In essence, the grouping and iterative looping in the regex is probably the slow part.

Of course, the console.info for each loop is also very slow.... and probably is something you added afterwards? If it is in your actual code, that's almost certainly the problem.

Let me explain the hard-parse with a code example:

var objParsed = {};
var lastKey;
var lines = str.split('\n');
for(var i = 0; i &lt; lines.length; i++) {
    var clause = lines[i].trim();
    if (clause.length == 0) {
        continue;
    }
    if (clause[0] == '[') {
        lastKey = {};
        objParsed[clause.substring(1, clause.length - 1)] = lastKey;
    } else {
        var pos = clause.indexOf("=");
        lastKey[clause.substring(0, pos)] = clause.substring(pos + 1);
    }
}


See the comparative results in this jsfiddle