JavaScript, elegant way to check nested object properties for null/undefined

JavascriptObjectJavascript Objects

Javascript Problem Overview

a "problem" which i have every now and then is that i have an object e.g. user = {} and through the course of using the app this gets populated. Let's say somwhere, after an AJAX call or something i do this:

user.loc = {
    lat: 50,
    long: 9

At another place i want to check if exists.

if ( {
    // do something

If it does not exists, this will cause an error. If is undefined, user.loc of course is undefined as well.

"Cannot read property 'lat' of null" - Dev Tools error

That means I need to check it like this:

if (user.loc) {
    if ( {
        // do something


if (user.loc && {
    // do something

This isn't really pretty and the bigger my objects are the worse it gets - obviously (imagine 10 levels of nesting). It kind bums me that if( isn't just returning false if user.loc is undefined as well.

What's the ideal way to check situations like this?

Javascript Solutions

Solution 1 - Javascript

You can use an utility function like this:

get = function(obj, key) {
    return key.split(".").reduce(function(o, x) {
        return (typeof o == "undefined" || o === null) ? o : o[x];
    }, obj);


 get(user, '')     // 50
 get(user, '') // undefined

Or, to check only if a property exists, without getting its value:

has = function(obj, key) {
    return key.split(".").every(function(x) {
        if(typeof obj != "object" || obj === null || ! x in obj)
            return false;
        obj = obj[x];
        return true;

if(has(user, '')) ...

Solution 2 - Javascript

You can combine the checks using lazy and:

if(user.loc && { ...

Or, you use CoffeeScript. And ES2020 has new syntax ( Nullish coalescing Operator ).

user.loc?.lat?. '...'

which would run the checks for loc property and safeguard against empty objects.

Solution 3 - Javascript

Well, javascript has try-catch. Depending on what you actually need to do (i.e. what your else statement would look like if it's undefined), that may be what you want.


try {;
} catch(error) {

Solution 4 - Javascript

Try this if(user && user.loc && {...}

You can check value of null and undefined using typeof

If .loc has value false than you can try

if(user && user.loc && typeof(user.loc)!=="undefined"){...}

If you have a huge nested object than have a look at


function checkNested(obj /*, level1, level2, ... levelN*/) {
  var args =,
      obj = args.shift();

  for (var i = 0; i < args.length; i++) {
    if (!obj.hasOwnProperty(args[i])) {
      return false;
    obj = obj[args[i]];
  return true;

var test = {level1:{level2:{level3:'level3'}} };

checkNested(test, 'level1', 'level2', 'level3'); // true
checkNested(test, 'level1', 'level2', 'foo'); // false

Update: Try lodash.get


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