Listing the available properties / functions for Date in JavaScript

Question

I am trying to list the properties / functions for Date in JavaScript using the below code:

var mydate=new Date();
for(var i in mydate){
   console.log(i);
}


        

Answer 1

Properties of date objects (or rather those that they inherit) are non-enumerable. Using Object.getOwnPropertyNames does reaveal them, so you can try this instead:

for (var o=new Date(); o!=null; o=Object.getPrototypeOf(o)) {
    console.log("on ["+o+"] itself:");
    Object.getOwnPropertyNames(o).forEach(function(p) {
        console.log(p)
    });
}

Alternatively, for checking the properties of native objects, you might just fire up their Docs - either in the spec or at MDN. Also, simply console.logging them usually produces an expandable view on an object that also includes the prototypes and their properties.

Answer 2

Many built-in objects have their methods set to not be enumerable, and therefore won't show up in a for..in loop.

You should instead look up some documentation, and then you can test if your browser supports certain things like:

if( 'now' in Date)