CODEWITHSUNDEEP
javascriptarrays
Rahmani Saif El Moulouk
Rahmani Saif El Moulouk

Reputation: 53

Insert array items into another array eventy nth elements

Here's the problem.

I have 2 arrays

Arrays :

var arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
var arr2 = ['up', 'down', 'left', 'right'];

I want to insert the arr2 elemments inside the arr1 every n step for example : 

/*
If the step is 2 the result would be : 
*/
[1,2,'up',3,4,'down',5,6,'left',7,8,'right',9, 10, 11, 12, 13, 14, 15, 16];

I have this function as a start point but I can't figure out how to solve my problem from : How to add item in array every x items?

/**
     * Add an item to an array at a certain frequency starting at a given index
     * @param array arr - the starting array
     * @param mixed item - the item to be inserted into the array
     * @param integer starting = the index at which to begin inserting
     * @param integer frequency - The frequency at which to add the item
     */
    function addItemEvery(arr, item, starting, frequency) {
      for (var i = 0, a = []; i < arr.length; i++) {
        a.push(arr[i]);
        if ((i + 1 + starting) % frequency === 0) {
          a.push(item);
          i++;
          if(arr[i]) a.push(arr[i]);
        }
      }
      return a;
    }

    var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
    arr = addItemEvery(arr, "item", 0, 3);
    console.log(arr);

Thank you so much for helping

Upvotes: 2

Views: 887

Answers (4)

Anna Pe
Anna Pe

Reputation: 1

I solved it that way

var arr2 = ['up', 'down', 'left', 'right'];
 
var arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];

var new_array = [];
var temp = 2;
var aggEl = () => {
    for(let i = 0, k=0; i<arr.length; i++){
        if(i== temp && k<arr2.length){
            new_array.push(arr2[k]);// I put the element of second array in new array
            k++;// I increase 'k' of one
            temp= i+3;   //new temp increase 'i' of 3 for find the new position where I will put other element of second array
        }
        else{      
            new_array.push(arr[i]);      
        }
    }
    alert(new_array);
}

Upvotes: 0

becher henchiri
becher henchiri

Reputation: 667

try this:

var arr1 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
var arr2 = ['up', 'down', 'left', 'right'];
var step=2;
var j=0;
 for (var i = 0,result= []; i < arr1.length; i++) {
         result.push(arr1[i]);
           if ((i + 1) % step === 0 && arr2.length>j)  {
            result.push(arr2[j]);
            j++;
          } 
    }
           console.log(result);

Upvotes: 0

ADyson
ADyson

Reputation: 62128

This is relatively simple to adapt:

1) set a counter to keep track of which items from the second array have been added

2) instead of simply adding "item" to the main array at the nth step, instead add the item from arr2 at the current count. Then increase the counter.

3) Change the if condition to ensure that it doesn't try to add more items than exist in arr2

Demo:

/**
     * Add an item to an array at a certain frequency starting at a given index
     * @param array arr - the starting array
     * @param array arr2 - the list of items to be inserted into the array
     * @param integer starting = the index at which to begin inserting
     * @param integer frequency - The frequency at which to add the item
     */
    function addItemEvery(arr, arr2, starting, frequency) {
      var arr2count = 0;
      for (var i = 0, a = []; i < arr.length; i++) {
        a.push(arr[i]);
        if ((i + 1 + starting) % frequency === 0 && arr2count < arr2.length) {
          a.push(arr2[arr2count++]);
          i++;
          if(arr[i]) a.push(arr[i]);
        }
      }
      return a;
    }

    var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
    var arr2 = ['up', 'down', 'left', 'right'];
    arr = addItemEvery(arr, arr2, 0, 2);
    console.log(arr);

Upvotes: 1

Gavin
Gavin

Reputation: 2365

This should get you on the right track. Note that this modifies the original arrays:

let arr1 = [1,2,3,4,5,6,7,8,9];
let arr2 = ['up', 'down', 'left', 'right'];
let nth = 2;
let result = arr1.reduce((carry, current_value, index, original)=>{
    // insert current element of arr1
    carry.push(current_value);
    // insert from arr2 if on multiple of nth index and there's any left
    if((index+1) % nth === 0 && arr2.length!=0){
        carry.push(arr2.shift())
    }
    return carry;
}, []);
console.log('result', result);

Upvotes: 2

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