My Javascript solution

    function kaprekarNumbers(p, q) { 

    // Write your code here

let array = [];

//find all numbers between the range of p and q and add them to an array 

for (let range = p; range <= q; range++) {
    array.push(range)
}

//get square numbers of that array 

let squared = array.map(num => num * num);

//create a second array to store the square roots of the square numbers that are equal to the two parts of the split square number (int1 + int2). The split and conversion from string and back to int is done in the for loop below, looping through the 'squared' array

let array2 = [];

for (let i = 0; i < squared.length; i++) {

    let str = squared[i].toString();
    let max = str.length;
    let str1 = str.slice(0, max / 2);
    let str2 = str.slice(max / 2, max);
    let int1 = parseInt(str1);
    let int2 = parseInt(str2);

    if (Math.sqrt(squared[i]) == (int1 + int2) || Math.sqrt(squared[i]) == squared[0]) {
        array2.push(Math.sqrt(squared[i]))
    }


}

if (array2.length == 0) {
    console.log('INVALID RANGE')
}

else {
    console.log(array2.join(' '))
}

}