Question

How do you declare namespace in javascript, explain with examples?

Answer 1

Even though JavaScript lacks namespaces, we can use Objects , IIFE to create namespaces.

1. Using Object Literal Notation: Let's wrap variables and functions inside an Object literal which acts as a namespace. After that you can access them using object notation

var namespaceOne = {
   function func1() {
       console.log("This is a first definition");
   }
}
var namespaceTwo = {
     function func1() {
         console.log("This is a second definition");
     }
 }
namespaceOne.func1(); // This is a first definition
namespaceTwo.func1(); // This is a second definition

1. Using IIFE (Immediately invoked function expression): The outer pair of parentheses of IIFE creates a local scope for all the code inside of it and makes the anonymous function a function expression. Due to that, you can create the same function in two different function expressions to act as a namespace.

(function () {
  function fun1() {
    console.log("This is a first definition");
  }
  fun1();
})();

(function () {
  function fun1() {
    console.log("This is a second definition");
  }
  fun1();
})();

1. Using a block and a let/const declaration: In ECMAScript 6, you can simply use a block and a let declaration to restrict the scope of a variable to a block.

{
  let myFunction = function fun1() {
    console.log("This is a first definition");
  };
  myFunction();
}
//myFunction(): ReferenceError: myFunction is not defined.

{
  let myFunction = function fun1() {
    console.log("This is a second definition");
  };
  myFunction();
}
//myFunction(): ReferenceError: myFunction is not defined.