Today I will share with you the simplest ways to reassign a variable if Null or Undefined in JavaScript. So, please read this article to the end to get more information.
Reassign a variable if Null or Undefined in JavaScript
First of all, we will find out when a variable is null
or undefined
in JavaScript. Check out the code below to get more information.
Code example:
let learnshare1;
console.log(learnshare1); // undefined
let learnshare2 = null;
console.log(learnshare2); // null
Output:
undefined
null
So you know when a variable is null
or undefined
, here we will start to learn the methods to reassign a variable if null
or undefined
in JavaScript.
Using the If check
In this method, we can check if a variable is null
or undefined
by using the If - else
method. If a variable is null
or undefined
, you will reassign a variable. Follow the code:
Code example:
let learnshare1;
// Check if undefined
if (learnshare1 === undefined) {
learnshare1 = "Updated successfully"; // Reassign a variable
console.log(learnshare1);
} else {
console.log("Not reassign");
}
let learnshare2 = null; // Initial a variable
// Check if null
if (learnshare2 === null) {
learnshare2 = "Updated successfully"; // Reassign a variable
console.log(learnshare2);
} else {
console.log("Not reassign");
}
Output:
Updated successfully
Updated successfully
Otherwise, you can shorten the code to make it clean code as follows:
let learnshare;
// Check if null or undefined
if (learnshare === null || learnshare === undefined) {
learnshare = "Updated successfully"; // Reassign a variable
console.log(learnshare);
} else {
console.log("Not reassign");
}
Output:
Updated successfully
Using the logical nullish assignment
Here, we will use a logical nullish assignment operator to reassign a variable if null or undefined.
First, we create a variable with the name learnshare, and then we will use a logical nullish assignment operator to assign a value for a learnshare variable. If a learnshare variable is null or undefined, it will not assign and keep value begin. Check out the code example below:
Code example:
let learnshare; // Initial a variable
// Use logical nullish assignment to check null or undefined and assign
learnshare ??= "updated successfully"
console.log(learnshare)
Output:
updated successfully
Summary
So, above are all the methods that I share with you to reassign a variable if Null or Undefined in JavaScript. If you have any questions, please leave a comment below. Thanks for reading, and good luck!

Hi, guys! My name’s Scott Miller. My current job is a software developer and I have shared a lot of quality articles about Javascript, C, C++, C#, Python, PHP, R, Java programming languages. I’m hoping they can assist you.
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