Chapter VI · Functions
Default Parameters
Default parameters allow standard initialization values to be assigned if no argument or undefined is passed.
01 How It Works
Think of a default setting checkbox pre-selected on an options menu screen.
If an argument is omitted during invocation, the engine falls back to the preset default value expression.
example.js
function greet(name = "Guest") {
console.log(`Hello, ${name}`);
}
greet(); // "Hello, Guest"1. Define a parameter in the function signature.
2. Assign a default fallback value using the equals sign (=).
3. Invoke without arguments to trigger the fallback.
02 Practical Example
Here is how you might see this concept applied in real-world code:
practical.js
function calculateTotal(price, tax = 0.05) {
return price + price * tax;
}Key Takeaway
Default parameters prevent unexpected undefined errors when arguments are omitted.