why is while causing an infinite loop?

Question

I'm testing out a selection sort but keep getting an infite loop.

Everything works fine when I have

while(arr.length > 3)

But when I make it any lower or change it to what it should be it causes an infinite loop in the code.

while(arr.length > 2)

Here is the rest of my code:

    let arr = [55,21,33,11,25]
    let newArr = [];
    let smallest = 999999999;
    let index;
    
    function selectionSort() {
    	while(arr.length > 2) {
    		//loops through the numbers array
    		for(i = 0; i < arr.length; i ++) {
    			// if the item is smaller, than pass it through
    			if(arr[i] < smallest) {
    				//change smallest to the arr[i]
    				smallest = arr[i]
    				index = i;
    			}
    		}
    		//remove the smallest number from the arr
    		arr.splice(index, 1)
    		//push the smallest number to the new arr
    		newArr.push(smallest)
    	}
    }
    
    selectionSort()

Have you debugged it? Stepping through it and tracking the values of all your variables at each stage? — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Mar 13, 2019 at 1:47

Kaiido · Accepted Answer · 2019-03-13 01:52:27Z

You need to reset smallest in each loop entries, otherwise once 11 is removed, other values will get compared against it and index never changes (3); and once index is greater than your array's length (at second iteration), your array is never spliced anymore.

let arr = [55, 21, 33, 11, 25]
let newArr = [];
let index;

function selectionSort() {
  while (arr.length > 2) {
    let smallest = Infinity;
    //loops through the numbers array
    for (i = 0; i < arr.length; i++) {
      // if the item is smaller, than pass it through
      if (arr[i] < smallest) {
        //change smallest to the arr[i]
        smallest = arr[i]
        index = i;
      }
    }
    //remove the smallest number from the arr
    arr.splice(index, 1)
    //push the smallest number to the new arr
    newArr.push(smallest)
  }
}

selectionSort()
console.log(newArr, arr)

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