how would I go about removing all circular references inside of an object? For example,

let certainObject = { abc: 'test' }
certainObject.prop = certainObject
removeCircular(certainObject)

would bee

{ abc: 'test' }

how would I go about removing all circular references inside of an object? For example,

let certainObject = { abc: 'test' }
certainObject.prop = certainObject
removeCircular(certainObject)

would bee

{ abc: 'test' }

• javascript

4 Answers 4

You need to iterate through the object, while keeping track of which objects you've already seen.

function removeCircular(obj) {
    const seen = new Map();
    const recurse = obj => {
        seen.add(obj,true);
        for( let [k, v] of Object.entries(obj)) {
            if( typeof v !== "object") continue;
            if(seen.has(v)) delete obj[k];
            else recurse(v);
        }
    }
    recurse(obj);
}

Note that this modifies the object in-place. If you want to keep the original object, you'll need to clone it first.

I would say something like:

function removeCircular(ref) {
    for (let i in ref) {
        if (ref[i] === ref) delete(ref[i]);
        else if (typeof ref[i] == 'Object') removeCircular(ref[i]);
    }
}

Or do you want this to work recursively? - edit, it is now recursive. However, this code could potentially end up in a loop. So the code of @NiettheDarkAbsol is better.

However, your example is not circular. You assign this to property, which is effectively the window object. If you want to have a circular object, you have to do:

certainObject = { abc: 'test' };
certainObject.propery = certainObject;

With such an example, my code works.

Just adding an updated version of Niet's answer that worked for me. And also because I can't ment/reply to Markus Knappen Johansson's question. :-P

The difference is using seen.set instead of seen.add. I'm guessing that .add is from another language?

function removeCircular(obj) {
  const seen = new Map();

  const recurse = obj => {
    seen.set(obj, true);

    Object.entries(obj).forEach(([k, v]) => {
      if (typeof v !== 'object') return;
      if (seen.has(v)) delete obj[k];
      else recurse(v);
    });
  };

  recurse(obj);
}

            var prams = {
                name: 'abc',
                obj : this,
                val : 'hello ',
               
            }
            

           

            function removecyclic(obj){
               newobj = {};
               for(key in obj){
                    if(typeof obj[key] == 'object'){
                        if(!obj.hasOwnProperty(key)){
                             newobj[key] = obj[key];
                            
                        }
                       
                        
                    }
                    else{
                        newobj[key] = obj[key];
                    }
                    
                }
                return newobj;
            }

           

           console.log(removecyclic(prams));