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Function Parameters & Arguments

Easy

In plain terms

Parameters are the names in the function definition. Arguments are the values passed when calling. JavaScript does not check the number - extra args are ignored, missing ones become undefined.

What you need to know

  • •Parameters = definition
  • •Arguments = call values
  • •No type or count checking

Try it yourself

Copy the code below and run it in your browser console or a code editor:

function greet(name, greeting) {
  return (greeting || 'Hello') + ', ' + name;
}
greet('Bob');           // "Hello, Bob"
greet('Bob', 'Hi');     // "Hi, Bob"
greet('Bob', 'Hi', 1);  // Extra arg ignored

// arguments object (legacy)
function sum() {
  let total = 0;
  for (let i = 0; i < arguments.length; i++) {
    total += arguments[i];
  }
  return total;
}

Learn more

Dive deeper with these trusted resources:

MDNjavascript.infoTutorialsPointW3Schools