Checking if a key exists in a JavaScript object?

Question

How do I check if a particular key exists in a JavaScript object or array?

If a key doesn\'t exist, and I try to access it, will it return false? Or throw an error?<

Answer 1

We can use - hasOwnProperty.call(obj, key);

The underscore.js way -

if(_.has(this.options, 'login')){
  //key 'login' exists in this.options 
}

_.has = function(obj, key) {
  return hasOwnProperty.call(obj, key);
};