You can get rid of the continue part since there is nothing else to do in that case anyway:
function removeHints(board, i, j) {
var elms = getHint(board, i, j);
for (var i = 0; i < elms.length; i++) {
if (!elms[i].classList.contains('show')) {
elms[i].classList.remove('hint');
elms[i].innerHTML = '';
}
}
}