Why won't the last array value be returned?-CodePudding

I have an array with several values and I want to get value stored in the multiple of 3. So, in this case the new array should be 13 and 28. However, I'm only getting 13.

Code:

    // array1 --> [ '5', '10', '13', '15', '20', '28' ]
    var trueLength = array1.length;
    var iCount = 1;
    for(var i = 0; i < trueLength;) {
        if(iCount % 3 != 0) {
            array1.shift();
        } else if (iCount % 3 == 0) {
            array2.push(array1[i]);
            array1.shift();
        }
        iCount  = 1;
        if(iCount == trueLength) break;
    }

Output:

[ '13' ]

I don't see anything logically wrong for it to only output 13 which makes no sense.

CodePudding user response：

array1.shift(); will remove the first element of the array. If you do this while iterating over iCount, you'll be skipping over some elements of the array, since you're both removing items and incrementing the index being iterated over.

Just filter the array by the modulo of the index being iterated over.

const arr = [ '5', '10', '13', '15', '20', '28' ];
const result = arr.filter((_, i) => i % 3 === 2);
console.log(result);

CodePudding user response：

you got little logical problem at break condition this would do


var array1 = ['5', '10', '13', '15', '20', '28'];
var array2 =[];

var trueLength = array1.length;
var iCount = 1;
    for(var i = 0; i < trueLength;) {
        if(iCount % 3 != 0) {
           
            array1.shift();
        } else if (iCount % 3 == 0) {
              console.log(iCount);
            array2.push(array1[i]);
            array1.shift();
        }
        iCount  = 1;
        if(iCount == trueLength 1) break;
    }
    
    console.log(array2[1]);

CodePudding user response：

If you like ti use the pattern of shift and neccessary pushign the value, you could use two variables to keep track of the length of the rest items and another for calculate the remainder..

const
    array = ['5', '10', '13', '15', '20', '28'];
    
let i = 1,
    l = array.length;

while (l) {
    const value = array.shift();
    if (i % 3 === 0) array.push(value);
    l--;
    i  ;
}

console.log(array);