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Difference Between Static and Const in JavaScript
Static variables can be defined as a class property that is used in a class and not on the class instance. This type of variable is stored in the data segment area of the memory. The value assigned to these types of variables is shared among every instance that is created in the class.
We need to use the static keyword for creating any static entity like a static variable, static function, operators, properties, etc. The value of a static variable is set at the runtime of the application and serves as a global value for the whole application.
Static Methods Example
In the example below, we are creating a static method and then accessing its value.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Static</title>
</head>
<body>
<h1 style="color: green;">
Welcome To Tutorials Point
</h1>
<script>
class example {
static staticMethod() {
return "I am a Static Method";
}
}
document.write(example.staticMethod());
</script>
</body>
</html>
I am a Static Method
Static Properties Example
Static properties belong to the class itself, not to instances:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Static Properties</title>
</head>
<body>
<script>
class Counter {
static count = 0;
static increment() {
this.count++;
}
}
Counter.increment();
Counter.increment();
document.write("Count: " + Counter.count);
</script>
</body>
</html>
Count: 2
Understanding Const Variables
Const - A constant can be defined as a variable that has a fixed defined value and remains the same throughout the program.
A property of the const variable is that we cannot change or modify this value anywhere in a project once it is initialized. It is because the compiler is informed about the fixed value and therefore should be prevented from any modifications.
Thus whenever any modification occurs in the const value an error is thrown instead of actual modification.
Basic Const Example
<!DOCTYPE html>
<html lang="en">
<head>
<title>Const</title>
</head>
<body>
<h1 style="color: green;">
Welcome To Tutorials Point
</h1>
<script>
const value = "I am a constant value";
document.write(value);
</script>
</body>
</html>
I am a constant value
Const Reassignment Error
Attempting to reassign a const variable throws an error:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Const Error</title>
</head>
<body>
<script>
const value = "Original value";
try {
value = "New value"; // This will throw an error
} catch (error) {
document.write("Error: " + error.message);
}
</script>
</body>
</html>
Error: Assignment to constant variable.
Key Differences
| Static | Constant |
|---|---|
| Static methods are used for creating a static copy of an object. | The const variable declares a constant value that cannot be modified |
| The static keyword is used for declaring the static method, variable, or operator | The const keyword is used for declaring the constant value. |
| Static is used with methods and classes. | We can use the const keyword with arrays and objects in JavaScript |
| The value of a static variable can be modified. | A constant value cannot be modified |
| Static is a storage specifier. | Const/Constant is a type qualifier. |
| Static can be assigned for reference types and set at run time. | Constants are set at compile-time itself and assigned for value types only. |
Conclusion
Static properties and methods belong to the class itself and are shared across all instances, while const variables create immutable references that cannot be reassigned. Both serve different purposes in JavaScript programming and are essential for different scenarios.
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