Check if a object is defined, best practice.

Question

I have the following JSON response from a ajax-request.

var json = {
    \"response\": {
        \"freeOfChargeProduct\": {  
        \"description\": \"Prod         


        

Answer 1

if(x && typeof x.y != 'undefined') {
    ...
}

// or better
function isDefined(x) {
    var undefined;
    return x !== undefined;
}

if(x && isDefined(x.y)) {
    ...
}

This will work for any data type in JavaScript, even a number that is zero. If you are checking for an object or string, just use x && x.y within the if statement, or if you already know that x is an object, if(x.y) ...