只有函数才有argumentsfunction fn(){console.log(arguments);console.log(arguments.length);console.log(arguments[2]);//我们可以按照数组的方式遍历argumentsfor (let i = 0; i < arguments.length; i++) {console.log(arguments[i]);}}fn(1,2,3);伪数组 并不是真正意义上的数组1. 具有数组的length 属性2. 按照索引的方式进行存储的3. 没有真正数组的一些方法利用函数求任意个数的最大值function getMax(){var max = arguments[0];for (var i = 1; i < arguments.length; i++) {if(arguments[i] > max){max  = arguments[i];}   }return max;}console.log(getMax(1,2,3));console.log(getMax(1,2,3,4,5));console.log(getMax(1,2,3,5,6,4,7));// 利用函数反转任意数组 reverse 翻转function reverse(arr){// 创建一个空数组var newArr = [];for (let i = arr.length - 1; i >= 0 ; i--) {newArr[newArr.length] = arr[i]}return newArr;}var arr1 = reverse([1,2,5,6,8,7,9]);console.log(arr1);var arr2 = reverse(['red','blue','green']);console.log(arr2);利用函数使数组冒泡排序  sort 排序function sort(arr){for (var i = 0; i < arr.length; i++) {for (var  j = 0; j < arr.length - i - 1; j++) {if (arr[j] > arr[j + 1]) {var temp = arr[j];arr[j] = arr[j+1];arr[j + 1 ] = temp;}                    }                }return arr;       }var ary1 =  sort([1,2,3,5,4,8,15,15,1548,8000])console.log(ary1);判断闰年的案例function isRunYear(year){// 设置返回的是true或者falsevar flag = false;if(year % 4 == 0  && year % 100 != 0 || year % 400 == 0){flag = true;}return flag;}console.log(isRunYear(2000));console.log(isRunYear(2001));