How to get function parameter names/values dynamically?

Question

Is there a way to get the function parameter names of a function dynamically?

Let’s say my function looks like this:

function doSomething(param1, par         


        

Answer 1

You can also use "esprima" parser to avoid many issues with comments, whitespace and other things inside parameters list.

function getParameters(yourFunction) {
    var i,
        // safetyValve is necessary, because sole "function () {...}"
        // is not a valid syntax
        parsed = esprima.parse("safetyValve = " + yourFunction.toString()),
        params = parsed.body[0].expression.right.params,
        ret = [];

    for (i = 0; i < params.length; i += 1) {
        // Handle default params. Exe: function defaults(a = 0,b = 2,c = 3){}
        if (params[i].type == 'AssignmentPattern') {
            ret.push(params[i].left.name)
        } else {
            ret.push(params[i].name);
        }
    }

    return ret;
}

It works even with code like this:

getParameters(function (hello /*, foo ),* /bar* { */,world) {}); // ["hello", "world"]