Recursive Descent Parser

function parse(input) {
	var i = 0;

	function descend(input) {
		var escape  = false,
			atom    = '',
			atomSet = [];

		for(i; i<input.length; i++) {
			
			switch(input[i]) {
				case '(':
					i += 1;
					atomSet.push( descend( input ) );

					break;
				case ')':
					if(atom.length > 0)
						atomSet.push(atom);
		
					escape = true;
					break;
				case ' ':
					if(atom.length > 0)
						atomSet.push(atom);

					atom = '';
					break;
				default:
					atom += input[i];
					break;
			}

			if(escape)
				break;

		}

		return atomSet;
	}

	return descend(input);
}

var t = parse("(a (b c))(d e f)");