Intro to JavaScript Dynamic vs Static Typed Languages

Learning objective: By the end of this lesson, students will understand the fundamental difference between dynamically-typed and statically-typed programming languages, with examples from JavaScript and C++.

Dynamically-typed languages such as JavaScript, Python, and Ruby allow variables to be assigned different types of data during runtime (as the program executes).

For example, in JavaScript, we can do this:

// Declare a variable named data and initialize with a number
let data = 123;
// Reassigning a different type of data is allowed
data = 'Hello';

However, statically-typed languages such as Java and C++ require a variable’s type to be declared and cannot be changed:

// Declare a variable as an integer and initialize it with an int
int data = 123;
// Assigning anything other than an integer raises an error
data = "Hello"; 
// NOT ALLOWED

📚 In a dynamically-typed language, the type of a variable can change at any time and is assigned a type based on whatever the variable’s value is at the time. In a statically-typed language, once a variable is given a type, that type cannot change.