Overview of null in javascript

Primitives and objects are the two categories of types in JavaScript. The strings, numbers, booleans, and symbols are called primitive data. The Complex data structures are called objects. The plain object is only a collection of keys and corresponding values. It is the most basic object in JavaScript, but occasionally it's impossible to make an object. JavaScript has a value called null, which denotes a missing object in multiple situations.

The special value null is contained in the primitive type null in JavaScript. The null value in JavaScript denotes the willful lack of any object values. A variable or method that returns null indicates that the desired object. It is not able to be constructed in the function.

Check the null value using javascript.

The javascript operator and object check whether the given value is null. The equality equator uses the "===" symbol to check given value is null. The non-equality equator uses the "!==" symbol to check value is null or not.

Use equality operator to check null value

//shows true as an output

Use equality operator to check null value

const first_var = null;
console.log(sec_obj !== null);

Example

The following example shows whether given objects are null or not using the equality or non-equality operator. The output shows in the Boolean format in the console tag. Using the javascript operator, you can see how the null value works with the object.

<!DOCTYPE html>
<html>
<head>
<title> Check value is null or not null using JavaScript </title>
</head>
<body>
<h3> Check value is null or not null using JavaScript </h3>
<p> See the console tab to display output. </p>
<script>
console.log("check value is null or not null using JavaScript");
const first_var = null;
const sec_obj = {
    width: 10
};
//shows true as an output
console.log(first_var === null); 
// shows false as an output
console.log(sec_obj === null); 
const third_obj = null;
console.log(third_obj !== null); 
const fourth_var = 20;
console.log(fourth_var !== null); 
</script>
</body>
</html>

Output

The following image shows null values output.

features of JavaScript null

The features listed below pertain to JavaScript null.

null is falsy
typeof null is an object

1) null is falsy

the False values include empty strings (''), undefined, NaN, and null apart from the 0 value. It implies that JavaScript will force null to false in conditional statements.

Syntax

The syntax shows the "null is falsy" below.

Var variable_name = 0;
OR
Var variable_name = undefined;

Example

The following example uses the operator to show whether given objects are null or not. You can see the different null values of the object with the "if" statement. The given object contains all formats of the null data then the "else" condition shows the output.

<!DOCTYPE html>
<html>
<head>
<title> Check value is null or not null using JavaScript </title>
</head>
<body>
<h3> Check value is null or not null using JavaScript </h3>
<p> See the console tab to display output. </p>
<script>
console.log("check value is null or not null using JavaScript");
const square_var = 20;
if (square_var) {
    console.log('The object value is not null');
} else {
    console.log('The object value is null');
}
const square_var1 = 0;
if (square_var1) {
    console.log('The object value is not null');
} else {
    console.log('The object value is null');
}
const square_var2 = NaN;
if (square_var2) {
    console.log('The object value is not null');
} else {
    console.log('The object value is null');
}
const square_var3 = undefined;
if (square_var3) {
    console.log('The object value is not null');
} else {
    console.log('The object value is null');
}
</script>
</body>
</html>

Output

The following image shows null values output.

2) The "typeof null" is an object

The "typeof" value shows the given format of the data. The null is a primitive value, not a javascript object. You can see the given object or null value as an output.

Syntax

The syntax shows the "typeof null" below.

Example

The example shows the "typeof null" below. Using a keyword, you can see whether the given values are null. The null values show the "object" as an output.

<!DOCTYPE html>
<html>
<head>
<title> Check value is null or not null using JavaScript </title>
</head>
<body>
<h3> Check value is null or not null using JavaScript </h3>
<p> See the console tab to display output. </p>
<script>
console.log("The null or not null value using JavaScript");
//display number
    console.log( typeof 10);
    //display string
    console.log( typeof 'stringdd');
    //display object to represent null
    console.log( typeof null);
</script>
</body>
</html>

Output

The following image shows null values output.

Replacement of the null

When you expect an item, null may occasionally emerge, frequently unexpectedly. JavaScript then throws an error if you attempt to obtain a property from null. Let's try to retrieve the content property from the given object using the javascript function.

Examples

The following examples show the replacement value of the javascript null values.

Example 1

The following example shows the replacement of the null values. The alternative message is displayed as an output.

<!DOCTYPE html>
<html>
<head>
<title> Check value is null or not null using JavaScript </title>
</head>
<body>
<h3> Check value is null or not null using JavaScript </h3>
<p> See the console tab to display output. </p>
<script>
console.log("The null or not null value using JavaScript");
let datas= '';
function nullObject(datas) {
console.log(datas?.message?? 'Welcome, Students!'); 
}
nullObject();  
</script>
</body>
</html>

Output

The following image shows an alternative to the null values output.

Example 2

The following example shows the replacement of the null values. The alternative message is displayed as an output. If the function shows a null value, the output shows default values.

<!DOCTYPE html>
<html>
<head>
<title> Check value is null or not null using JavaScript </title>
</head>
<body>
<h3> Check value is null or not null using JavaScript </h3>
<p> See the console tab to display output. </p>
<script>
console.log("The null or not null value using JavaScript");
function nullObject(datas) {
  if (!datas) {
    datas = 'Students';
  }
  console.log( "message: Please Attend the Sheet!"+ datas);
}
nullObject('Devid'); 
nullObject();  
</script>
</body>
</html>

Output

The following image shows an alternative to the null values output.

Example 3

The following example shows the trap of the null values. here, you can use the null or undefined value.

<!DOCTYPE html>
<html>
<head>
<title> Check value is null or not null using JavaScript </title>
</head>
<body>
<h3> Check value is null or not null using JavaScript </h3>
<p> See the console tab to display output. </p>
<script>
console.log("The null or not null value using JavaScript");
function nullObject(datas) {
  if (!datas) {
    datas = ' ';
  }
  console.log( "message: Please Attend the Sheet!"+ datas);
}
nullObject();  
</script>
</body>
</html>

Output

The following image shows an alternative to the null values output.

The difference between undefined vs. null

An uninitialized variable's or object property's value is undefined.

As a syntax, if a variable is declared without an initial value, accessing that variable evaluates to undefined:

let myVarData;
Console.log( myVarData); // => undefined

Null denotes a missing item, but undefined denotes an uninitialized state, and these two concepts are fundamentally different.
Null and undefined are distinguished by the rigorous equality operator ===:

// output shows false
Console.log( null === undefined );

Although the ad hoc equality operator == regards null and undefined as being equal:

// output shows true
Console.log( null == undefined );

JavaScript common null error

You frequently call a function to obtain an object in JavaScript. After, you can access that object's property.
You will get a TypeError if the function provides null rather than an object. See the following syntax:

In this syntax, we choose an element with the id saves and get to its varList attribute.
querySelector('#save') returns null if there are no elements on the page with the id save. As a result, retrieving the className attribute with the null value returns an error: