arguments.length

The arguments.length data property contains the number of arguments passed to the function.

Value#

A non-negative integer.

{{js_property_attributes(1, 0, 1)}}

Description#

The arguments.length property provides the number of arguments actually passed to a function. This can be more or less than the defined parameter's count (see {{jsxref("Function.prototype.length")}}). For example, for the function below:

function func1(a, b, c) {
  console.log(arguments.length);
}

func1.length returns 3, because func1 declares three formal parameters. However, func1(1, 2, 3, 4, 5) logs 5, because func1 was called with five arguments. Similarly, func1(1) logs 1, because func1 was called with one argument.

Examples#

Using arguments.length#

In this example, we define a function that can add two or more numbers together.

function adder(base /*, num1, …, numN */) {
  base = Number(base);
  for (let i = 1; i < arguments.length; i++) {
    base += Number(arguments[i]);
  }
  return base;
}

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• Functions guide
• Functions
• {{jsxref("Functions/arguments", "arguments")}}
• Function: length