Yes, Constants exist in JavaScript. We use the keyword const for constants. The value of const remains the same; you cannot change and declare it again. Create a read-only reference with the const declaration.
The const is introduced in ES6. Before ES6, we used to declare variables using var keywords only. Later, let, and const are introduced. Now, we will see in detail about const.
const value = "some-value";With const, you can declare local variables with block scope rather than function scope. Let’s say we have a constant variable a. After declaring a value like a constant variable, you can’t assign a new value to it
// declared ‘a’ as a constant variable.
const a = 150;
// Assigning a new value to `a` will fail since ‘a’ is a constant
variable
a= 0;
a++;
// The below declarations won’t work
var a = 0;Constants are block-scoped, much like variables declared using the const keyword. Constants cannot be changed by using assigning and can’t be declared again. However, if we have arrays and objects as constant, we can modify and remove the elements, but we cannot declare them again.
Example 1
We can start variable names with upper case and also the lower case for const.
<!DOCTYPE html>
<html>
<body>
<h2>Const</h2>
<p id="demo"></p>
<script>
const num = 34;
document.getElementById("demo").innerHTML = num;
</script>
</body>
</html>Const values can’t be reassigned
We can’t reassign constants to new values. When we try to reassign, it will throw an error. Let’s see an example
