Question

I am trying to learn JavaScript. After reading this page: What does ':' (colon) do in JavaScript?

I tried to replace

var store = new dojo.data.ItemFileReadStore({
         url: "countries.json"
 });

with

var store = new dojo.data.ItemFileReadStore();
        store.url = "countries.json";

It does not work. Can any one please point out the mistake, or explain the correct use of the Colon operator?.
Thanks.

Answer 1

That’s not a fair comparison, although you’re almost there.

var store = new dojo.data.ItemFileReadStore({
         url: "countries.json"
 });
//Creates a new store object, passing an anonymous object in with URL
// property set to "countries.json"

The alternative without the colon operator is:

var props={};
props.url="countries.json"
var store = new dojo.data.ItemFileReadStore(props);
//Does same as above but doesn't use :

Not this isn’t the only use of : in JavaScript though, it can also be used in the ternary operator (alert(b==c?'equal':'not equal');) and in labels (for example in case statements)