jackjop jackjop - 1 year ago 44
Javascript Question

Specifying which parameter to pass

Consider that I have a method like below, in C#.

void DoSomething(bool arg1 = false, bool notify = false)
{ /* DO SOMETHING */ }

I can specify which parameter I pass to method like this:

DoSomething(notify: true);

instead of

DoSomething(false, true);

Is it possible in Javascript?

Answer Source

It's not possible, but you can workaround it by passing objects and adding some custom code

 * This is how to document the shape of the parameter object
 * @param {boolean} [args.arg1 = false] Blah blah blah
 * @param {boolean} [args.notify = false] Blah blah blah
function doSomething(args)  {
   var defaults = {
      arg1: false,
      notify: false
   args = Object.assign(defaults, args);

doSomething({notify: true}); // {arg1: false, notify: true}

And you could generalize this

createFuncWithDefaultArgs(defaultArgs, func) {
    return function(obj) {
        func.apply(this, Object.assign(obj, defaultArgs);

var doSomething = createFuncWithDefaultArgs(
    {arg1: false, notify: false}, 
    function (args) {
         // args has been defaulted already


Note that Object.assign is not supported in IE, you may need a polyfill