What I am looking for is basically a hasOwnProperty() or 'in' function which is recursive and looks down the chain to see if a key or property exists in an object.

For example I have the object:

var user = {
  username: "Derpette",
  profile: {
    role: 'admin',
    sex: 'female',
    emails:['[email protected]']
    }
}

I want to know if there is a key/property 'role' anywhere in the object or its sub-objects. So I want to be able to call something like user.hasProperty('role') and it would return true.

Right now I am using if statements with a chain of assertions to check but it doesn't seem clean, especially for deep nested properties.

For example I would do:

if(user && user.profile && user.profile.role){
    //Manipulate/Use user.profile.role here
}

Another example of a use-case for this is if I am filtering mongoDB update modifiers ing from a client. I want to make sure they aren't updating their own role so I need to check that the property 'role' isn't somewhere in their mongoDB modifier json object. But it could be in a few places in a modifier so doing the if property chaining doesn't work well for this case.

Do I need to write my own recursive hasOwnProperty? I am thinking that something like this should already exist somewhere in a project like jquery or underscores.js or sugar.js but I can't seem to find it.

What I am looking for is basically a hasOwnProperty() or 'in' function which is recursive and looks down the chain to see if a key or property exists in an object.

For example I have the object:

var user = {
  username: "Derpette",
  profile: {
    role: 'admin',
    sex: 'female',
    emails:['[email protected]']
    }
}

I want to know if there is a key/property 'role' anywhere in the object or its sub-objects. So I want to be able to call something like user.hasProperty('role') and it would return true.

Right now I am using if statements with a chain of assertions to check but it doesn't seem clean, especially for deep nested properties.

For example I would do:

if(user && user.profile && user.profile.role){
    //Manipulate/Use user.profile.role here
}

Another example of a use-case for this is if I am filtering mongoDB update modifiers ing from a client. I want to make sure they aren't updating their own role so I need to check that the property 'role' isn't somewhere in their mongoDB modifier json object. But it could be in a few places in a modifier so doing the if property chaining doesn't work well for this case.

Do I need to write my own recursive hasOwnProperty? I am thinking that something like this should already exist somewhere in a project like jquery or underscores.js or sugar.js but I can't seem to find it.

• javascript
• object
• recursion
• properties

• I'm pretty sure there isn't one. But you could easily make a function that does so – Ian Commented Jul 30, 2013 at 21:21
• For example: jsfiddle/N82aZ/2 – Ian Commented Jul 30, 2013 at 21:24

2 Answers 2

You could do this recursively:

function recHasProp(obj, prop) {
    for (var p in obj) {
        if (obj.hasOwnProperty(p)) {
            if (p === prop) {
                return obj;
            } else if (obj[p] instanceof Object && recHasProp(obj[p], prop)) {
                return obj[p];
            }
        }
    }
    return null;
}

Usage:

var obj = recHasProp(user, 'role');
if (obj) {
    // obj.role exists, and obj is user or a child of user
}

My take on this, it's not pretty, but it's very performant in the few lines that it is.

function hasProp(obj, propPath, i) {
      if (typeof(i) === 'undefined' && !(i=0)) {
        propPath = propPath.split('.');
      }
      if (typeof(obj[propPath[i]]) !== 'undefined') {
        return (++i && i !== propPath.length) ? hasProp(obj[propPath[i - 1]], propPath, i) : true;
      }
      return false;
};

Usage Example (in your case):

hasProp(user, 'profile.role');

Plunker: http://plnkr.co/edit/CIePivi3XcTEugFzEUyt?p=preview