How to prevent JavaScript object from mutating?

 In this post we will look in to a way to prevent object from mutating. Using only const will not effectively prevent an obj form mutating.

So what we need to use is a method called Object.freeze().

 This method will prevent any attempt at changing the object and will throw an error if the code is running in strict mode. 

let obj = {

  1: "apple",

  2: "banana",

  3: "chocolate",

};

Object.freeze(obj);

try {

  obj[10] = "vanilla";

  console.log(obj);

  // { '1': 'apple', '2': 'banana', '3': 'chocolate' } vanilla was not added

// to the object.

 

} catch (error) {

  console.log(error); // this will be fired when running in strict mode

}

When we use the freeze method on the obj and try to add vanilla, It was not added.