比较第一个数组中的元素位置与第二个数组中的数字

Question

I am trying to compare the two arrays, more specifically to do something with values from the first one whose positions matches the numbers from second one.

var valuesList = ['value1', 'value2', 'value3', 'value4', 'value5'],
    positionNumberList = [0, 2, 4];

from above arrays value1 should be eq to 0 from second one, value3 = 2 .etc

I started with the code below but can not get the position of the values from the first array.

for(j=0; j < valuesList.length; j++){

   for(k=0; k < positionNumberList.length; k++){
       //find matching values from first array                     
   }
}

Answer 1

One of the solutions is use map() method which applies a provided callback function for every item from array .

 var valuesList = ['value1', 'value2', 'value3', 'value4', 'value5'], positionNumberList = [0, 2, 4]; console.log(positionNumberList.map(function(item) { return valuesList[item]; })); 

Answer 2

To do this you only need a single loop to iterate through the positionNumberList array, and then access the items in valuesList with the given indexes, like this:

 var valuesList = ['value1', 'value2', 'value3', 'value4', 'value5']; var positionNumberList = [0, 2, 4]; positionNumberList.forEach(function(index) { var value = valuesList[index]; console.log(value); }); 

Answer 3

Another approach:

var valuesList = ['value1', 'value2', 'value3', 'value4', 'value5'],
    positionNumberList = [0, 2, 4];


if(positionNumberList.length < valuesList.length){
     for(var i=0; i < positionNumberList.length; i++){
         console.log(positionNumberList[i],valuesList[i])
     }
}
else{
    for(var i=0; i < valuesList.length; i++){
         console.log(valuesList[i],positionNumberList[i])
     }
}

https://jsfiddle.net/xrjjxmbn/