JavaScript Default_params Guide
Default function parameters allow functions to be called with fewer arguments by specifying fallback values. The guide walks through Default Parameters. `function greet(name = "Guest") { }` — default if undefined. `function log(msg, prefix = new Date().toISOString()) { }` — computed default. Defaults are evaluated at call time. Only applies to undefined (not null). Earlier params can be used in later defaults: `function(a, b = a + 1)`. Defaults work with destructuring: `function({x = 0} = {})`. The guide is organized into 1 sections that build on each other, each pairing a prose explanation with runnable code. Related guides: Arrays, Strings, Numbers, Math, Date. This is one of 145 JavaScript guides on JS Reference — see the full list on the guides page. Practice what you learn in the JavaScript playground, and look up any unfamiliar term in the JavaScript glossary.