如何确定返回的 javascript 对象

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?

Answer 1

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");
}

Answer 2

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.

Answer 3

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.