What is Null in JavaScript?
Within the realm of JavaScript, the concept of null denotes the deliberate nonexistence of a value linked to any object. Despite being classified as a primitive type, there are scenarios where null demonstrates object-like behavior.
Put differently, the concept of null signifies the intentional lack of a specific object value. It is a basic value that represents the non-existence of a value or acts as a placeholder for an object that is not currently available.
A distinction exists between null and undefined, indicating a variable that has been defined but not yet given a value.
Syntax
The syntax of null in JavaScript is as follows:
let number = null;
console.log("Type of number is:", typeof number);
Use Cases of Null in JavaScript
Object initialization
In JavaScript, if the creation of an object is unsuccessful, it will typically result in the return of null, which is a frequent outcome.
class Square {
constructor(length){
this.length = length;
}
static createSquare(length){
return length > 0 ? new Square(length) : null;
}
}
const square1 = Square.createSquare(10); //it will create a valid Square object
const square2 = Square.createSquare(); //it will return null
console.log(square1);
console.log(square2);
Output:
Square { length: 10 }
null
Checking for null
In JavaScript, the null value is utilized to signify the deliberate absence of a value.
const myValue = null;
if (myValue) {
console.log("Not null"); // This won't execute
} else{
console.log("Null"); // it will return null
}
Output:
How to Check for Null in JavaScript
To verify for null in JavaScript, a straightforward method involves recognizing that null results in false in conditionals or when coerced to a Boolean value.
const maybeNull = null
if(maybeNull) { console.log("Not null") } else { console.log("Could be null") } // Could be null
for(let i = 0; null; i++) { console.log("Won't run") }
maybeNull ? console.log("truthy value") : console.log("Falsy value") // falsy value
Let?s explore using the double equality == and triple equality === equality operators to check for null.
Double Equality operator
In JavaScript, one method to validate null is by verifying if a value is loosely equivalent to null through the double equality == operator.
Example
console.log("The 7 falsy values")
0 ? console.log("truthy") : console.log("falsy") // falsy
0n ? console.log("truthy") : console.log("falsy") // falsy
null ? console.log("truthy") : console.log("falsy") // falsy
undefined ? console.log("truthy") : console.log("falsy") // falsy
false ? console.log("truthy") : console.log("falsy") // falsy
NaN ? console.log("truthy") : console.log("falsy") // falsy
"" ? console.log("truthy") : console.log("falsy") // falsy
console.log("The value null")
console.log(null==0) // false
console.log(null==0n) // false
console.log(null==null) // true
console.log(null==undefined) // true
console.log(null==false) // false
console.log(null==NaN) // false
console.log(null=="") // false
It is beneficial for verifying the lack of a value: both null and undefined signify the absence of a value and are loosely equal, indicating they hold the same value despite being distinct types.
When programming, it is essential to verify whether a variable contains a value before proceeding with any operations on it. Utilize the ==null to ascertain if the variable is either null or undefined.
Triple Equality Operator ===
In JavaScript, when we want to specifically check for a null value while excluding any undefined values, we should use the triple equality === operator, also referred to as the strict equality operator.
Example
console.log("The value null")
console.log(null===0) // false
console.log(null===0n) // false
console.log(null===null) // true
console.log(null===undefined) // false
console.log(null===false) // false
console.log(null===NaN) // false
console.log(null==="") // false
In general, it is advisable to handle both null and undefined values because they both indicate the absence of a value.
Verifying for null is a situation in JavaScript where using == is advisable. In other cases, the === operator, known as triple equality, can also be employed.
Using the object.is Function
The object.is function in JavaScript allows for the comparison of two values to determine if they are identical. It returns a Boolean value indicating whether the two parameters provided to the function are equal. It is important to note that this comparison considers two values to be equal if both are null.
Syntax
Object.is( q, null);
Parameters
What is a variable that is initialized with a null value and passed into a function?
Null: this parameter is a null value.
Algorithm
In the initial step, a variable named q is defined with a value of null.
In the second step, following this action, we provide the input q and a null value. We then utilize the object.is method within an if-statement to ascertain their equality.