js array Case

1. seek array [2,6,1,7, 4] inside and the average value of all elements.
     

  // (1) declare a variable sum sum. 
        @ (2) traverse the array, each array element which is added to the sum inside. 
        @ (3) with variable sum divided by the sum of the length of the array can be an array of average value. 
        var ARR = [2,. 6,. 1,. 7,. 4 ];
         var SUM = 0 ;
         var Average = 0 ;
         for ( var I = 0; I <arr.length; I ++ ) {
            SUM + = arr [i]; // plus the array element arr [i] is not counter I 
        }
        average = sum / arr.length;
        the console.log (SUM, Average); // wants to output a plurality of variables, separated by commas

2, find the maximum value array [2,6,1,77,52,25,7] in

        var arr = [2, 6, 1, 77, 52, 25, 7, 99];
        var max = arr[0];
        for (var i = 1; i < arr.length; i++) {
            if (arr[i] > max) {
                max = arr[i];
            }
        }
        the console.log ( 'which is the maximum value of the array:' + max);

3, the array [ 'red', 'green', 'blue', 'pink'] is converted to a string, and a | or other code division
 

       // 1. The need for a new variable for storing the conversion completes string str. 
        // 2. traversing the original array, which are the data taken out, which was added to the string. 
        // 3. At the same time behind one more separator 
        var ARR = [ 'Red', 'Green', 'Blue', 'Pink' ];
         var STR = '' ;
         var On Sep = '|' ;
         for ( var I = 0; I <arr.length; I ++ ) {
            str += arr[i] + sep;
        }
        console.log(str);

4, a new array, stored inside an integer of 10 (1-10)

        // core principle: use a loop to append the array. 
        // 1, declare an empty array arr. 
        // 2, the loop counter i can be stored as array elements. 
        // 3, the array index number is zero-based, and therefore more appropriate counter starting at 0, into the array element to +1. 
        var ARR = [];
         for ( var I = 0; I <100; I ++ ) {
             // ARR = I; not directly assigned to the name of the array or previous element gone 
            ARR [I] = I +. 1 ;
        }
        console.log(arr);

5, the array [2, 0, 6, 1, 77, 0, 52, 0, 25, 7] equal to greater than the elected element 10, into the new array.

        // 1, declare a new array used to store new data newArr. 
        // 2, traversing the original old array to find the element 10 is greater than or equal. 
        // 3 sequentially added to the new array newArr. 
        // Method. 1 
        var ARR = [2, 0,. 6,. 1, 77, 0, 52 is, 0, 25,. 7 ];
         var newArr = [];
         var J = 0 ;
         for ( var I = 0; I <ARR .length; I ++ ) {
             IF (ARR [I]> = 10 ) {
                 // new array index should be in ascending order starting from 0 
                newArr [J] = ARR [I];
                j++;
            }
        }
        console.log(newArr);
        // Method 2 
        var ARR = [2, 0,. 6,. 1, 77, 0, 52 is, 0, 25,. 7 ];
         var newArr = [];
         // beginning newArr.length is 0 
        for ( var I = 0 ; I <arr.length; I ++ ) {
             IF (ARR [I]> = 10 ) {
                 // new array index should be sequentially incremented from 0 
                newArr [newArr.length] = ARR [I];
            }
        }
        console.log(newArr);

6, the array [ 'red', 'green', 'blue', 'pink', 'purple'] Content stored in turn

        // 1, declare a new array newArr 
        // 2, the old array index No. 4 to take over (arr.length - 1), to the new index of the array element 0 (newArr.length) 
        // 3, we taken decreasing manner i-- 
        var ARR = [ 'Red', 'Green', 'Blue', 'Pink', 'Purple', 'HotPink' ];
         var newArr = [];
         for ( var I = arr.length -. 1; I> = 0; i-- ) {
            newArr[newArr.length] = arr[i]
        }
        console.log(newArr);