How to Check For Object Properties in JavaScript

How to Check If Object Property is Null or Undefined in JavaScript ?

let obj = {
  name : 'Hari',
  info : {
    country : 'India'
  }
}

In the above code, obj.name returns Hari since the key name exists. If you try to access a non existent key from obj, like, obj.info.gender it will throw undefined.

Now let’s say if the value of gender is undefined since it doesn’t exists we need to show some default value, like Not specified. You can do,

let obj = {
  name : 'Hari',
  info : {
    country : 'India'
  }
};
let gender = obj.info && obj.info.gender ? obj.info.gender : "Not specified";

Now let’s rewrite the above checking using Optional Chaining,

let obj = {
  name : 'Hari',
  info : {
    country : 'India'
  }
};
let gender = obj.info?.gender ?? "Not specified";

And at the end we have used ?? (Nullish Coalescing Operator) to check if null or undefined and in such cash return a default value.