Best way to check if a number contains another number

Convert to string and use indexOf

(752+'').indexOf('5') > -1

console.log((752+'').indexOf('5') > -1);
console.log((752+'').indexOf('9') > -1);

Convert to string and use one of these options:

indexOf():

(number + '').indexOf(needle) > -1;

includes():

(number + '').includes(needle);