JavaScript Functions

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Section 4 of 4

Parameters and Arguments

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Parameters and Arguments

Topic Overview

Take your time to understand each concept. Practice with the examples below!

Functions become really powerful when they can accept and work with different inputs. Let's learn how to make flexible functions!

Parameters vs Arguments:

•
Parameters:Variables listed in the function definition (the placeholders)
•
Arguments:Actual values passed when calling the function

Example:

function greet(name, age) {  // 'name' and 'age' are parameters
  return `Hi ${name}, you are ${age} years old`;
}
greet("Sam", 25);  // "Sam" and 25 are arguments

Default Parameters (backup values):

function greet(name = "Friend") {
  return `Hello, ${name}!`;
}
greet();        // "Hello, Friend!" (uses default)
greet("Amy");   // "Hello, Amy!" (uses provided value)

Rest Parameters (accept any number of inputs):

function sum(...numbers) {  // ...numbers collects all arguments
  let total = 0;
  for (let num of numbers) {
    total += num;
  }
  return total;
}
sum(1, 2, 3);      // 6
sum(5, 10, 15, 20); // 50