Javascript Object Method every developer should know!

let obj = {}; = "dhoni"; obj.year= 2020; obj.speak = function(){ return "My Name is "" and this is year "+this.year;}

Here you can see the name, year and speak properties. In JS methods are also properties with type function. Lets begin

Before we start, lets check out a typical object initialization in JS.

let newObj = obj; obj.year= 2021; console.log(newObj.year) // 2021 console.log(newObj.speak()) // My Name is dhoni and this is year 2021

You can create a shallow copy i.e. a top level properties copy, using Objects.assign{} method.

Copying an Object

Shallow Copy

let copyObject = Object.assign({} ,newObj); = "kohli"; console.log(copyObject.speak()); // My Name is kohli and this is year 2021 console.log(newObject.speak()); // My Name is dhoni and this is year 2021

let deepCopyObj = JSON.parse(JSON.stringify(obj)); console.log(deepCopyObj); // {name: 'dhoni', year: 2019 }

Object.create() function has additional flexibility that you can choose what will be prototype of your new object.

Deep Copy


let createObj = Object.create(obj); console.log(createObj);  //{} = "PK" console.log(createObj.speak()); // My Name is PK and this is year 2021

if you just need to copy only properties that are not functions- there is an efficient method. We are moving away from Object constructor here and using another global object in JS- JSON

let person = {name: "Roger" , age: 30) let entries = Object.entries(person); console.log(entries); // [  [  'name', 'Roger'  ],  [  'age', 30  ]  ]

this function picks only keys (or property labels) of objects and returns an array.



let keys = Object.keys(person); console.log(keys); //  [  'name',  'age'  ]

Object.entries() method returns an array of key-value pairs of object's enumerable properties.

let values = Object.values(person); console.log(values); //  [  'roger',  30  ]


This function picks only values of objects and returns an array.

let frozenObject = Object.freeze(person); = "tendulkar"; console.log(frozenObject); // {  name:  'Roger'.  age:  30  }

Object.freeze( )

This function freezes the object for any further changes (key or values). It may throw any error (unless you are in strict mode) but there will be no effect of value change on your object.

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