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arguments Object

arguments Object

Introduction

The arguments object is an array-like object accessible inside functions that contains all arguments passed to the function. It’s available in regular functions (not arrow functions).

Example

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

console.log(sum(1, 2, 3, 4)); // 10

Array-like, Not an Array

function test() {
  console.log(arguments.length); // 3
  console.log(arguments[0]); // 'a'
  console.log(arguments[1]); // 'b'

  // ❌ arguments.map is not a function
  // ✅ Convert to array
  const args = Array.from(arguments);
  // or
  const args = [...arguments];
}

test('a', 'b', 'c');

Not Available in Arrow Functions

const arrowFn = () => {
  console.log(arguments); // ReferenceError
};

Summary

arguments contains all passed arguments
It’s array-like (has length, indexed), not a real array
NOT available in arrow functions
Prefer rest parameters ...args in modern code

Further Reading

MDN: arguments