Understanding const vs let

2020-02-02

In JavaScript, const and let are both ways to declare variables, but they have some important differences.

const stands for "constant." When you declare a variable using const, you are telling the compiler that the value of the variable cannot be reassigned. For example:

const pi = 3.14;
pi = 3.14159; // This would cause an error

On the other hand, let allows you to declare a variable whose value can be reassigned. For example:

let x = 5;
x = 10; // This is allowed

One important thing to note is that const does not mean that the value of the variable is immutable (i.e., cannot be changed). For example, if you have a const variable that is an array or an object, you can still change the elements or properties of that array or object.

const arr = [1, 2, 3];
arr.push(4); // This is allowed
arr = [1, 2, 3, 4, 5]; // This would cause an error

In general, it is a good practice to use const whenever you know that a variable will not need to be reassigned, as it can help to prevent accidental reassignments and make your code easier to understand. let should be used when you need to reassign a variable.