InsertionSort.js

function InsertionSort(arr) {

  let len     = arr.length,     	// number of items in the array
	    value,                      // the value currently being compared
	    i,                          // index into unsorted section
	    j;                          // index into sorted section
	
	for(i = 1; i < len; i++) {

		// store the current value because it may shift later
		value = arr[i]
		j = i - 1

	  // Whenever the value in the sorted section is greater than the value
	  // in the unsorted section, shift all items in the sorted section over
	  // by one. This creates space in which to insert the value.
		while (j >= 0 && arr[j] > value) {
			arr[j+1] = arr[j]
			j--
		}
		arr[j+1] = value
	}

	return arr

}