Default Parameters

When you pass `undefined` to a parameter with a default value, the default value is used. JavaScript treats explicitly passing `undefined` the same as not passing a value at all for that parameter. This is a key aspect of how default parameters work. For example, in `function greet(name = 'Guest') { return `Hello, ${name}`; }`, calling `greet(undefined)` will result in `'Hello, Guest'`. This behavior allows you to selectively use default values even in the middle of a parameter list—you can pass `undefined` as a placeholder to use a default while providing values for later parameters. This is different from passing other falsy values like `null`, `false`, `0`, or an empty string, which are treated as intentional values and will override the default parameter values.