Default Parameters

Function parameters can have default values used when the argument is undefined.

Example

function greet(name = "World", punct = "!") {
  return `Hello, ${name}${punct}`;
}
greet();          // "Hello, World!"
greet("Alice");   // "Hello, Alice!"
greet("Bob", "."); // "Hello, Bob."
// Defaults can reference earlier params
function range(start, end = start + 10) { return [start, end]; }

JAVASCRIPT

Full Editor

Pro Tip

Default parameters are evaluated at call time, not definition time — safe for expressions.

Related Resources

JavaScript Reference

Complete tag & property list

JavaScript How-To Guides

Step-by-step practical guides

JavaScript Exercises

Practice what you've learned