function problem4(){
    let product = 1;
    let largest = 1;
    for(let i = 999; i>=100; i--){
        for(let j = 999; j>=i && i*j>largest; j--){
            product = i*j;
            if(("" + product) == ("" + product).split("").reverse().join("")){
                largest = Math.max(largest, product);}
}
    }
    return largest;
}
console.log(problem4());