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Tag Archives: Javascript


Today, we are going to expose some inner working of angular 2.

You know what, the double curly braces aka interpolation always  seems awesome magic.

<h1>{{ text }} </h1>

Really, this is sugar syntax for:

<h1 [innerText]=”text”></h1>

Yeah… angular 2 property binding using DOM attribute directly. So, is it possible to add class to a div tag?? Well

<h1 [className]=”active”></h1>

This is equivalent to

h1 = document.querySelector(‘h1’);
h1 = ‘active’;  // className is property of DOM element div

Interesting, isn’t it?

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Pass by value and pass by reference is age old concept. It is working similar way in JavaScript too. If you like to see some code so that you can understand better. Keep reading.

Brief theory before jump into code. JavaScript primitive types (string, number, boolean, null and undefined) are passed by value. Whereas non-primitive types (objects, arrays, functions, etc.) are passed by reference.

// Primitive types: Immutable by default
let x = 5
let y = x
y = 10
console.log(x) // output 5
console.log(y) // output 10

// Non-primitive types: Mutable
let animal = {
    name: 'Rat'
}
let anotherAnimal = animal
anotherAnimal.name = 'Horse'
console.log(animal) // {name: "Horse"}
console.log(anotherAnimal) // {name: "Horse"}
console.log(animal === anotherAnimal) // true

This knowledge might be useful while learning react.js, redux architecture.


It is common in forms, to get user inputs for numerical calculations later like house rent allowance for salary calculation. In such scenarios, the value returned is string which if we add result in concatenation. To avoid this mistake adding toInt method to string object directly will be handy.

/**
 * adding toInt method to String object
 * author rajakvk <rajakvk at gmail dot com>
 */
if(!String.toInt) {
  /**
   * Returns integer value if a string value is passed.
   * @name toInt
   * @methodOf String
   * @param {*} none 
   * @returns {Number}
   */
  String.prototype.toInt = function() {
     return parseInt(this, 10);
  }
}
// Usage
// $('#hra').val().toInt();
// typeof $('#hra').val();  // string
// typeof $('#hra').val().toInt();  // number

Note: This method converts string to Integer discarding decimal places.