How to deep clone JavaScript objects efficiently

Learn how you can implement fast deep cloning of objects in JavaScript.

When you’re writing a clone function in JS, you should consider a case when one of the source fields is an object itself.

If that’s the case, you need to recursively clone that object as well.

function clone(obj) {
  var clone = {};
  for(var i in obj) {
    if(obj[i] != null &&  typeof(obj[i]) == "object")
      clone[i] = clone(obj[i]);
    else
      clone[i] = obj[i];
  }
  return clone;
}

For convenience, you can add the clone function to the Object.prototype.

Object.defineProperty(Object.prototype, "clone", { value: clone, enumerable: false });

This will allow you to use the clone function on all JS objects.

If you’re looking for a prebuilt solution, you can use the lodash function.