Skip to content

JavaScript: Loosely Typed Language

JavaScript is known as a loosely typed (or weakly typed) language. This means that variables in JavaScript are not bound to any specific data type. You can assign any type of value to a variable, and you can even change its type at any time during the program.

Loosely Typed Explained

In strictly typed languages (like C or C++), you must declare the type of a variable, and it can only store values of that type:

// C language example
int a;
a = 10;        // ✔ Valid
a = "Hello";   // ✖ Error: Cannot assign string to int

In JavaScript, variables are flexible:

var a;
a = 10;           // a is now a number
a = "Hello";      // a is now a string
a = true;         // a is now a boolean

You can reassign different types of values to the same variable without any errors!

Example: Changing Types in JavaScript

Here's a step-by-step example:

var a;
console.log("Step 1, a =", a); // undefined

a = 10;
console.log("Step 2, a =", a); // number

a = "Hello World";
console.log("Step 3, a =", a); // string
Console Output
Step 1, a =  undefined
Step 2, a =  10
Step 3, a =  Hello World

Key Takeaway

  • Loosely typed means you don't need to declare variable types.
  • Variables can change their type at runtime.
  • This provides flexibility, but you need to be careful to avoid type-related bugs