描述

Arguments对象的属性length声明了传递参数给当前函数的参数个数。该属性只在函数体内被定义。
注意，这个属性声明的是实际传递给函数的参数个数，而不是期望传递的参数个数。有关声明的参数个数，请参阅属性"Function.length"。还要注意，该属性不具备Array.length属性的专有行为。

例子

function check(args){
  var actual = args.length;//The actual number of arguments
  var expected = args.callee.length; //The expected number of arguments
  if(actual != expected){    //Throw exception if they don't match
    throw new Error("Wrong number of arguments: expected: "+
   expected + "; actually passed " + actual);
  }
}
//A function that demonstrates how to use the function above
function f(x,y,z) {
  check(arguments);  //Check for correct number of arguments
  return x + y + z;  //Now do the rest of the function normally
}

参阅

Array.length,  Function.length