How to determine what javascript object has been returned

Question

In instances when a javascript function returns an object, what is a good way of determining what exactly it is that you got?

If I do this:

alert(myFunction(this));

And I get back simply [object Object], what are some useful things that I can do to determine what it is?

Is this just for debugging, or would you actually want the program to know some details about the object? — OliverRadini, Oct 05 '15 at 21:17
see story http://stackoverflow.com/questions/957537/how-can-i-display-a-javascript-object — inic, Oct 05 '15 at 21:22

score 2 · Accepted Answer · answered Oct 05 '15 at 21:22

if debugging don't use alert, use the console instead

console.log(myFunction(this));
console.dir(myFunction(this));
console.error(myFunction(this));
//etc

If you are trying to determine the type of object and do something depending on what it is use typeof or instanceof

Using typeof

var something = myFunction(this);
if(typeof something === "string"){
   console.log("It's a string");
}

Using instanceof

var something = myFunction(this);
if(something instanceof HTMLElement){
    console.log("It's an html element");
}

Zakaria Acharki · Answer 2 · 2015-10-05T21:31:17.600

Use console.log method to display data in your console instead of alert :

console.log(myFunction(this));

In some browsers you can use console.dir, so you can get more details about the object :

console.dir(myFunction(this));

Example

var myObj = {foo: 'bar'}

alert(myObj);

console.log(myObj); //Check your console, you can see the object
console.dir(myObj); //You can see the object with more details

Hope this helps.

score 0 · Answer 3 · answered Oct 05 '15 at 21:26

Example: http://jsfiddle.net/6daL71zd/

You can use:

1)

console.log(myFunction(this))

to print out to the console

(this can be accessed via your browser's developer tools...the 'F12' key on your keyboard should open it)

2)

var output = document.createTextNode(JSON.stringify(myFunction(this)));
document.body.appendChild(output);

to print out on the page.

How to determine what javascript object has been returned

3 Answers3