数组的遍历 ​

var a = [1,2,3,4,5,6,7,8,9];
for(var i = 0;i<a.length;i++){
    console.log(a[i]);
}

var a = [1,2,3,4,5,6,7,8,9];
for(var i in a){
    console.log(a[i]);
}

var a = [1,2,3,4,5,6,7,8,9];
var i = 0;
while(i<a.length){
    console.log(a[i]);
    i++
}

#数组升序
<script>
    var arr = [2,20,30,5,0,54,222,55,51,36,25,0,3,5,52,25,102]
    for (var i=0;i<=arr.length-1;i++){            //外层循环趟数
        for (var j=0;j<=arr.length-i-1;j++){      //里面循环管每一次交换次数
            if (arr[j]>arr[j+1]){
                var temp=arr[j]
                arr[j]=arr[j+1]
                arr[j+1]=temp
            }
        }
    }
    console.log(arr)
</script>

#数组降序
<script>
    var arr = [2,20,30,5,0,54,222,55,51,36,25,0,3,5,52,25,102]
    for (var i=0;i<=arr.length-1;i++){            //外层循环趟数
        for (var j=0;j<=arr.length-i-1;j++){      //里面循环管每一次交换次数
            if (arr[j]<arr[j+1]){
                var temp=arr[j]
                arr[j]=arr[j+1]
                arr[j+1]=temp
            }
        }
    }
    console.log(arr)
</script>

#数组求和及平均数
<script>
    var arr = [1,2,3,4,5,6,7,8,9]
    var k = 0
    for (var i=0;i<arr.length;i++){
        console.log(arr[i])
        k += arr[i]
    }
    console.log("arr数组的和为：",k)
    console.log("arr数组的平均数为：",k/arr.length)
</script>

#数组求max
<script>
    var arr = [1,2,3,4,5,6,7,8,9]
    var max = arr[0]
    for (var i=0;i<arr.length;i++){
        if (arr[i] > max){
            max = arr[i]
        }
    }
    console.log("arr数组的max为：",max)
</script>
#求min及"arr[i] < max"

#将1~10加到数组里面
<script>
    var arr = []
    for (var i=1;i<=10;i++){
        arr[i-1] = i
    }
    console.log(arr)
</script>

#取出数组里面特定的数放到另一个数组里面(大于50的数放到newArr里面)
<script>
    var arr = [2,20,30,5,0,54,222,55,51,36,25,0,3,5,52,25,102,]
    var newArr = []
    for(var i=0;i<arr.length;i++){
        if (arr[i]>50){
            newArr[newArr.length]=arr[i]
        }
    }
    console.log(newArr)
</script>

#数组的去重,去掉0然后保存到新数组
<script>
    var arr = [2,20,30,5,0,54,222,55,51,36,25,0,3,5,52,25,102,]
    var newArr = []
    for(var i=0;i<arr.length;i++){
        if (arr[i]>50){
            newArr[newArr.length]=arr[i]
        }
    }
    console.log(newArr)
</script>

#数组的反转
<script>
    var arr = [2,20,30,5,0,54,222,55,51,36,25,0,3,5,52,25,102,]
    var newArr = []
    for(var i=arr.length-1;i>=0;i--){
        newArr[newArr.length]=arr[i]
    }
    console.log(newArr)
</script>