CODEWITHSUNDEEP
javascriptarraysloopssplice
Tobi
Tobi

Reputation: 93

Is there a way to add elements with .splice() during a loop in javascript?

I have an array like this: 

[0, 24.646213151927437, 27.737256235827665, 29.08326530612245]

I want to fill every space between the elements which are greater than 4 with random numbers. Like this:

var arr = [0, 24.646213151927437, 27.737256235827665, 29.08326530612245];
var length = arr.length;
for (var j = 0; j < length;) {
  var spacebetween = arr[j + 1] - arr[j];
  if (spacebetween > 4) {
    // fill the space until the sum of numbers is greater than space between
    var m = Math.random() * (3 - 1 + 1);
    for (k = m; k < spacebetween;) {
      arr.splice(j, 0, parseFloat(k));
      m = Math.random() * (3 - 1 + 1);
      k = k + m;
    }
  }
  j++;
}
console.log(arr);

The problem is with splice(), the index is shifting and I have no idea how to solve this. The new numbers should stay in ascending order within the array.

Upvotes: 1

Views: 691

Answers (2)

Mister Jojo
Mister Jojo

Reputation: 22320

Is there a way to add elements with .splice() during a loop in javascript?

Yes, the solution is to simply start from the end and decrement, the new entries will no longer disturb the process:

changed with no gap greater than 4

let arr = [ 0, 24.646213151927437, 27.737256235827665, 29.08326530612245 ]

for (let j=arr.length; --j;)   // inside loop j start to (arr.length-1) to value==1  ( value zéro mean false)
  {
  let vRef = arr[j-1]
   ,  vMin = arr[j] -4  
   ;
  while (vMin > vRef) 
    {
    vMin = (Math.random()*4) + vMin
    arr.splice( j, 0, vMin )
    vMin -= 4
    }
  }

console.log( JSON.stringify( arr,0,2 ))
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 0

Katherine R
Katherine R

Reputation: 1158

Instead of looping through the array (with a changing length), you can use a reduce to loop through the original array and push updates to the accumulator 

var arr = [0, 24, 27, 29];
var newArr = arr.reduce((accumulator, cur, i) => {
    var needTempArr = arr[i + 1] && (arr[i + 1] - cur);

    // if need temp array, generate it; otherwise, empty array
    var tempArr = needTempArr
        ? Array(needTempArr).fill(0).map(() => Math.random())
        : [];


    return accumulator.concat(cur, tempArr);
}, []);

Upvotes: 1

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