function.length代表函数定义的参数个数

function.arguments.length函数实际传递的参数个数

如下:

function recursive10to2Int(n)
{
 window.alert(recursive10to2Int.length);
 window.alert(recursive10to2Int.arguments.length);
}

recursive10to2Int();

recursive10to2Int(1);

recursive10to2Int(1,2);
function.length

Description

length is a property of a function object, and indicates how many arguments the function expects, i.e. the number of formal parameters. This number does not include the rest parameter. By contrast, [arguments.length](https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Functions_and_function_scope/arguments/length "JavaScript/Reference/Functions_and_function_scope/arguments/length") is local to a function and provides the number of arguments actually passed to the function.

Example



console.log( (function () {}).length ); / 0 /
console.log( (function (a) {}).length ); / 1 /
console.log( (function (a, b) {}).length ); / 2 etc. /
console.log( (function (…args) {}).length ); / 0, rest parameter is not counted /