// 封装indexOf(两个值，第一个数组，第二个要查找的内容，第三个值是从哪里开始找)

var arr = ["w","e","g","f","g"];
function fingIndex( array, con, star){
isNaN(star)? i = 0 : i =star;
for ( i; i < array.length; i++){
if( array[i] == con){   
return i;
} //循环去判断
}return -1;
}console.log( fingIndex(arr,"g",''))//2

封装一个reverse函数

 var arr = [1, 4, 5, 6, 7, 7, 9];
 function isArray (array){ 
 var b = []
 var len = array.lenght 
 if( array instanceof Array){          //要求判断参数是否是数组
 for ( i = 0; i < len; i++){
 b.unshift(arr[i])  
 }
 }else{
 console.log("请输入一个正确的数组")
 }
 }
 console.log (isArray(arr))

冒泡排序(从大道小)

    function  maopao(arr){
      var len = arr.length;
      for (var i = 0; i < len - 1; i++) {
        for(var j = 0;j < len - 1 - i; j++){
          if (arr[j] > arr[j+1]) {
            var num = arr[j];
            arr[j] = arr[j+1];
            arr[j+1] = num
          }
        }
      }
      return arr
    }
    console.log(maopao(arr))