JSFiddle - React, Tailwind, and code Playground

JavaScript

var numbers = new Array();
/*
for(var i = 0; i < 5000; i++) {
    if(i == 701 || i == 893) {
        continue;
    }
    numbers.push(i);
}
*/
numbers = [ 1,2,3,4,5,6,7,8,9,
10,11,12,13,14,15,16,17,18,19,
20,21,22,23,24,25,27,28,29,
30,31,32,33,34,36,37,38,
42,43,44,45,47,
50,51,52,57,58,59,
61,62,63,64,65,66,67,68,69,
70,71,72,73,74,75,76,77,78,79,
80,81,82,83,84,85,86,87,88,89,
90,91,92,93,94,95,96,97,98,99,100 ];

    function findMissing(arr, start, stop) {
        
        var current = start,
            next = stop,
            collector = new Array();
        
        function parseMissing(a, key) {
            if(key+1 == a.length) return;
            
            current = a[key];
            next = a[key + 1];
            
            if(next - current !== 1) {
                collector.push(current + 1);
                // insert current+1 at key+1
                a = a.slice( 0, key+1 ).concat( current+1 ).concat( a.slice( key +1 ) );
                return parseMissing(a, key+1);
            }
            
            return parseMissing(a, key+1);
        }
        
        parseMissing(arr, 0);
        return collector;
    }

var catches = findMissing(numbers, 1, 100);
console.log(catches);