Javascript function always returns null

Question

I am newbie to the JavaScript world. I have a doubt how the return statement works in JavaScript.

What I am trying to do is to have a function pass one arguments

Answer 1

Try this:

function exampleFunction(param){ 
    return exampleData[param];
  }

EDIT: If you want to return null if the parameter is undefined, then take a look at Paul and Crazy Train's comments:

return (typeof exampleData[param] === 'undefined')? null: exampleData[param]; 

OR

return (param in exampleData) ? exampleData[param] : null;