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//声明一个函数，具有3个形参：a,b,c
function whatever(a,b,c) {
//值的准确性检验
assert(a===1,"The value of a is 1");
assert(b===2,"The value of b is 2");
assert(c===3,"The value of c is 3");
//共传入5个实参。
assert(arguments.length ===5,"We've passed in 5 parameters");
//验证传入的签3个实参与函数的3个形参匹配
assert(arguments[0]===a,"The first arguments is assigned to a");
assert(arguments[1] ===b, "The second argument is assigned to b");
assert(arguments[2]===c,"The third argument is assigned to c");
//验证额外的参数可以通过参数arguments获取。
assert(arguments[3]===4,"We can access the fourth argument");
assert(arguments[4]===5 ,"We can access the fifth argument");
}
//调用函数时闯入5个参数
whatever(1,2,3,4,5);
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即时这里的whatever函数只定义了3个形参，但在调用的时候传入了5个参数；whatever(1,2,3,4,5);
function whatever(a,b,c) {
...
}
我们可以通过对应的函数参数a,b和c访问到前3个参数的值；
assert(a===1,"The value of a is 1");
assert(b===2,"The value of b is 2");
assert(c===3,"The value of c is 3");
我们还可以使用arguments.length属性来获取传递给函数的实际参数的个数。
通过数组下标的方式还可以访问到arguments参数的每个参数值。值得注意的是，这个也包括没有和函数形参相关联的剩余参数。
assert(arguments[0]===a,"The first arguments is assigned to a");
assert(arguments[1] ===b, "The second argument is assigned to b");
assert(arguments[2]===c,"The third argument is assigned to c");
assert(arguments[3]===4,"We can access the fourth argument");
assert(arguments[4]===5 ,"We can access the fifth argument");
arguments不是一个一个数组。你可能会被它的用法误导，毕竟他有length属性，而却可以通过数组下标的方式访问到每个元素。但它并非JavaScript数组，如果你尝试在arguments对象上使用数组的方法
如（sort方法），会发现最终会报错。arguments对象仅仅是一个类数组的结构，在使用中要尤为注意。