Hashbang Comments - The Third Way of Adding Comments in Javascript Code

Until lately, Javascript had 2 types of comment syntax — one for adding single line comments and one for adding multi-line comments.

// this is single line comment

/* this is 
a multi-line 
comment */

However recent updates to Javascript have introduced a third type of comment syntax. This is the hashbang comment syntax.

Hashbang Comments in LINUX Operating Systems

Hashbang / shebang are commonly used in LINIX operating systems. Text files with hashbang start with #! characters sequence, and they specify the interpreter that is used to execute the file. For example :

• This will will execute the file using the Bourne shell.

  #!bin/sh
  
  // contents of the file
  

• This will will execute the file using the Bash shell.

  #!bin/bash
  
  // contents of the file
  

Hashbang Comments in Javascript

The hashbang comment syntax has now been added in Javascript also. This can be added to the start of a script or module to specify the path of the Javascript interpreter that is to be used to execute the containing code. The comment can be contained only in a single line.

#!/path-to-v8/v8-shell

// Javascript code that will be executed by the V8 interpreter

This syntax is useful for Javascript executing on the server-side. Servers can have multiple Javascript interpreters, and using the hashbang syntax we can choose a specific interpreter to execute our Javascript code..