JavaScript named arguments

named-arguments.js

callWithNamed({one: 1, two: 2, three: 3}, function(three, one, two) {
    console.log(one, two, three);
});


function callWithNamed(dict, fn, context) {
    var newArgs = [];
    var parsedArgs = parseArgs(fn);
    for (var i = 0; i < parsedArgs.length; i++) {
        var name = parsedArgs[i];
        if (typeof dict[name] === 'undefined') {
            console.warn('Arg %s is missing on', name);
        }
        newArgs[i] = dict[name];
    }
    fn.apply(context || null, newArgs);
}


function parseArgs(fn) {
	var str = fn.toString();
    var startIndex = str.indexOf('(') + 1;
    var endIndex = str.indexOf(')', startIndex);
    var argsStr = str.slice(startIndex, endIndex);
    return argsStr.split(',').map(function(name) {
        // TODO: strip comments
        return name.trim();
    });
}