Question

Possible Duplicate:
How do I test for an empty Javascript object from JSON?

var test= {};

var incidentReport = {
      "place1": "n/a",
      "place2": "n/a",
      "place3": "n/a",
 }

Above are the two ways my varible is going to look. Ive tryed doing the following code to test if its empty/looks like {}

if(test == "")

and tried

if(test == null)

also tried

if(!test)

Does anyone know where I am going wrong? Just a beginner to JavaScript and JSON. Is what I am doing considered back practice are there better ways to declare this empty?

Thanks for the support

Answer 1

if(test == "")

checks if it is an empty string, so this won’t work

if(test == null)

checks if it is null which is “similar” to undefined – this isn’t the case

if(!test)

checks if it is a falsy value, this in not the case either.

You have to check if there exist child-elements (properties):

function isEmpty(obj) {
    for(var prop in obj) {
        if(obj.hasOwnProperty(prop)) return false;
    }
    return true;
}

if ( isEmpty(test) ){...}

The very important point is the .hasOwnProperty() – this checks if it is a real property of the object and not only inherited through the prototype chain.