Functions | Learning Resources

Short explanation

Functions are fundamental units of behavior in JavaScript. They can be declared, expressed, or created as arrow functions — each with subtle semantics (like this binding) that affect how they behave on invocation.

Syntax examples

// Declaration
function greet(name) {
  return `Hello, ${name}`;
}

// Function expression
const multiply = function (a, b) {
  return a * b;
};

// Arrow function
const add = (a, b) => a + b;

How JS handles it internally

When a function is called, JavaScript creates an execution context containing the function's scope, arguments, and local variables. The function's [[Environment]] (closure) determines which variables it can access. Arrow functions differ by not creating their own this binding and inheriting this from the outer scope.

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FAQ

Q: What's the main difference between arrow functions and declarations?

A: Arrow functions don't have their own this, arguments object, or prototype. They are best for concise callbacks and when you want lexical this.

Q: Are functions objects?

A: Yes — functions in JavaScript are first-class objects and can have properties and be passed around like values.