How to name JavaScript Identifiers?

Javascript Web Development Front End Technology

In this tutorial, we will learn how to name JavaScript Identifiers.

Identifiers in JavaScript are the names we give to variables, arrays, objects, functions, etc

We must give the names unique to identify them properly. There are some rules we must follow to name the identifiers that are common to most languages.

Rules for naming Identifiers

There are certain rules we have to follow before naming an identifier. A proper name helps the programmer to make the code more effective. The rules are the following −

JavaScript identifier names should not start with any numeric values like 0-9. For example, 0xyz, and 87b are invalid names.
Identifier names should start with an alphabet, dollar ($), or underscore character. For example, Abc9, _abc, $pq is a valid one.
Excluding the first character, the rest of the name can include letters, numbers, dollar($), or underscore. But we cannot include any special characters including space (#, @, “ ”) other than underscore.
JavaScript Identifier names are case sensitive: for example- Abc, ABC, aBc, abc these all are the name of different variables.
There are some reserved keywords in JavaScript. Those are called reserved words. We cannot choose these keywords to make an identifier name. This makes the compiler confused. For example: break, let, new, boolean, etc. are not valid variable names.

The list of reserved keywords in JavaScript are −

abstract	arguments	await	boolean
break	byte	case	catch
char	class	const	continue
debugger	default	delete	do
double	else	enum	eval
export	extends	false	final
finally	float	for	function
goto	if	implements	import
In	instanceof	int	interface
Let	long	native	new
null	package	private	protected
public	return	short	static
super	switch	synchronized	this
throw	throws	transient	true
Try	typeof	var	void
volatile	while	with	yield

Suggestions to make a good identifier name

Make the Identifier names descriptive. In a long code using names with one word (like a, b, etc) could not help you to remember what is this variable used for. But too much lengthy names are inefficient. Up to 20 characters with 2 to 4 words are enough to make a decent identifier name.
Use multiple words to name an Identifier to make it descriptive.
Blank spaces are not allowed in identifier names. We can name them Camel case (like firstName) or use underscore (like first_name) to make it more readable.
As JavaScript Identifiers are case sensitive make sure you did not make multiple variables with the same name but different cases (upper or lower). That makes the programmer confused and ends up with errors.

Syntax

//Assigning value to a variable
let Identifier_name = Value;
//Assigning value to function
function Identifier_name(){
   //statement
}

In the above syntax, we used two kinds of identifiers - variable and function. To assign a value first, we declare the variable name with the let keyword. Then we assigned the value using assigning operator. And in the function, we named a function name the put the line of codes inside the function.

Example 1

In the below example, we will learn about how to name a variable identifier and initialize them with values, and access them.


<html>
<body>
   <h3> Showing different types of <i> variable Identifier values </i>
   </h3>
   <div id="root"> </div>
   <script>
      // initializing variables with values
      let number = 5; //variable to store number
      let string = "Hello World"; //variable to store string
      let bool = true; //variable to store boolean
      document.getElementById('root').innerHTML = "number:" + number +
      "<br/>" + "string:" + string + "<br/>" + "boolean:" + bool
   </script>
</body>
</html>

Example 2

In the below example, we will learn about how to name an array and object identifier and initialize them with values, and access them. For showing the object values as a string we used JSON.stringify() method.


<html>
<body>
   <h3> Showing <i> array and object Identifier values </i> </h3>
   <div id="root"> </div>
   <script>
      let arr = ["apple", "banana", "mango"]; //array
      let obj = { Productname: "book", price: 200 }; //object
      document.getElementById('root').innerHTML = "array: " + arr + "<br/>"
      + "object: " + JSON.stringify(obj)
   </script>
</body>
</html>

In this tutorial, we learned how can we name JavaScript Identifiers. We learned some basic theories of identifiers. In the two examples, we see used variables, arrays, and object identifiers and output their values in the webpage.