Introduction to JavaScript Objects

  • Everything in JavaScript is an Object
  • Just like object in anyother language, it has its own properties and methods
  • We can check the list of methods available for an object in the proto section of the object
  • “window” is a built in object of the browser, it the mother of all object on the browser.
  • “window” object is the object of the browser in which you are executing the command

Using browser console to perform object creation :

  • In above example we have created an array object
  • As we type the object name “names” in the console we could expand it and see the properties in that object, in our case length is the property of that object
  • The proto section in the above screenshot displays the methods available for that object.

Calling a property of an object

Calling a method on an Object

Example 2 : For Objects.

Data Types :

  • There are 6 primitive data types: string, number, bigint, boolean, undefined, and symbol.
  • There also is null, which is seemingly primitive, but indeed is a special case
  • Most of the time, a primitive value is represented directly at the lowest level of the language implementation.
  • All primitives are immutable, i.e., they cannot be altered.
  • It is important not to confuse a primitive itself with a variable assigned a primitive value.
  • The variable may be reassigned a new value, but the existing value can not be changed in the ways that objects, arrays, and functions can be altered.
  • Since primitive data types are not object technically you shouldn’t be able to run methods on those but JavaScript is a bit smart i.e it wraps the Primitive data types into an object when you going to execute some methods on primitive data types

Example :

// Using a string method doesn't mutate the string
var bar = "baz";
console.log(bar);               // baz
console.log(bar);               // baz

// Using an array method mutates the array
var foo = [];
console.log(foo);               // []
console.log(foo);               // ["plugh"]

// Assignment gives the primitive a new (n

Primitive Wrapper Object in JavaScript :

Except for null and undefined, all primitive values have object equivalents that wrap around the primitive values:

  • String for the string primitive.
  • Number for the number primitive.
  • BigInt for the bigint primitive.
  • Boolean for the boolean primitive.
  • Symbol for the symbol primitive.

The wrapper’s valueOf() method returns the primitive value.

Example of a Primitive String :

Example of a Primitive String wrapped in an Object :

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