CODEWITHSUNDEEP
javascriptobject
JustcallmeDrago
JustcallmeDrago

Reputation: 1883

Check if object member exists in nested object

Is there a simpler way than using ___ in object to check the existence of each level of an object to check the existence of a single member?

More concisely: How can I check if someObject.member.member.member.value exists?

Upvotes: 27

Views: 15417

Answers (8)

kmonsoor
kmonsoor

Reputation: 8109

If you can use lodash library, it has a very elegant solution, hasIn.

_.hasIn(someObject, 'member.level1.level2.level3');

for example,

var obj = {'x': 999, 'a': {'b': {'c': 123, 'd': 234}}}
// => undefined

_.hasIn(obj, 'x')
// => true

_.hasIn(obj, 'a.b.d')
// => true

_.hasIn(obj, 'a.b.e')
// => false

Upvotes: 0

ojreadmore
ojreadmore

Reputation: 1475

Check out lodash-deep’s deepHas https://github.com/marklagendijk/lodash-deep#_deephascollection-propertypath

And this too https://github.com/danielstjules/hoops

Upvotes: 3

Ben
Ben

Reputation: 1213

Theres a safeRead function defined here on thecodeabode which allows a safeRead of nested properties i.e.

safeRead(foo, 'bar', 'jim', 'jam');

if any of the properties are null or undefined a blank string is returned - useful for formatting / string interpolation

Upvotes: 2

Oscar Gillespie
Oscar Gillespie

Reputation: 117

You could also try/catch TypeError?

try {
  console.log(someObject.member.member.member.value);
} catch(e) {
  if (e instanceof TypeError) {
    console.log("Couldn't access someObject.member.member.member.value");
    console.log(someObject);
  }
}

Upvotes: 7

Felix Kling
Felix Kling

Reputation: 816462

In general, you can use if(property in object), but this would be still cumbersome for nested members.

You could write a function:

function test(obj, prop) {
    var parts = prop.split('.');
    for(var i = 0, l = parts.length; i < l; i++) {
        var part = parts[i];
        if(obj !== null && typeof obj === "object" && part in obj) {
            obj = obj[part];
        }
        else {
            return false;
        }
    }
    return true;
}

test(someObject, 'member.member.member.value');

DEMO

Upvotes: 36

Michael Lorton
Michael Lorton

Reputation: 44386

Something like (warning: untested code ahead)

var testProperty = function(obj, proplist) {
   for (var i=0; i < proplist.length; i++) {
      if (obj.hasOwnProperty(proplist[i])) {
         obj = obj[proplist[i]];
      } else {
        return false;
      }
   }
   return true;
}

Upvotes: 2

user113716
user113716

Reputation: 322502

Here's one way: http://jsfiddle.net/9McHq/

var result = ((((someObject || {}).member || {}).member || {}).member || {}).value;

alert( result );

Upvotes: 4

Phrogz
Phrogz

Reputation: 303253

if (someObject.member && someObject.member.member &&
    someObject.member.member.member && someObject.member.member.member.value) ...

or similarly:

var val = foo.bar && foo.bar.jim && foo.bar.jim.jam && foo.bar.jim.jam.value;

This will not 'work' if any particular value happens to be null, false, 0, or "" (an empty string), but with the possible exception of the final value, this seems unlikely to be the case.

Also, note that typeof ____ !== "undefined" is not the correct test to see if an object has a property. Instead you should use ___ in object, e.g. if ("member" in someObject). This is because you can set a property to an explicit value of undefined, which is different from removing it with delete someObject.member.

Upvotes: 2

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