Advanced JavaScript Backend Basics

JavaScript programming language that is usually used for web scripting. It is a lightweight, interpreted programming language. JavaScript is one of the most programming languages for web development. For running JavaScript each browser has its own engine which enables the proper functioning of JavaScript in the browser. Some common Browsers and their JavaScript engines are −

  • Spider Monkey for firefox
  • V8 for Google Chrome
  • JavaScript code for Safari
  • Chakra for Microsoft Internet Explorer/ edge

To make JavaScript universe and stop a browser from describing their own scripts. There is a standard set for JavaScript which will be used throughout the browser. there is an Association named ECMA ( European computer manufacturers Association) which sets standards for JavaScript.

How JavaScript engine works?

For proper running of JavaScript code, the JavaScript engine works in two different phases to make sure the script created work properly irrespective of the browser.

  • Creation phase − In the creation phase, the JavaScript engine well goes through the entire code and check the syntax of the program and throw a synthetic error if it occurs. the engine will declare and provide some memory chunks to variables as well as to the functions that are declared in the JavaScript code.

  • Execution phase − in the execution phase, the engine will run the code. Also, the variables are declared and throw any other error that may occur.

JavaScript “==” Vs “===” operator

In JavaScript, there are two types of equality operators.

== operator is used to test for checking abstract equality of two values. This means in this comparison the equality of values is checked, the type of data is not checked for equality.

=== operator is used to check for strict equality of two values. This means in this comparison both types and equality of the data are checked.


document.write(34 == "34");
document.write(98 === "98");



JavaScript Boolean Values

Boolean variables are those variables in programming languages that have only two types of values. The valid boolean values in Javascript programming language are TRUE and FALSE.

The TRUE value in programming corresponds to the values other than 0, which triggers the conditional statements in Javascript.

Some values that convert back to TRUE boolean value are −

  • {} - empty object
  • [] - empty array
  • !False values are TRUE

FALSE values in programming correspond to 0 values, that does not ignore conditional statements in Javascript.

Some values that convert back to FALSE boolean value are −

  • 0 - numerical value of FALSE
  • undefined - value that is undefined is false
  • null - null value is always false

Updated on: 16-Oct-2019


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