Join class names

clsx.js

function toVal(mix) {
  var k, y, str='';
  if (typeof mix === 'string' || typeof mix === 'number') {
    str += mix;
  } else if (typeof mix === 'object') {
    if (Array.isArray(mix)) {
      for (k=0; k < mix.length; k++) {
        if (mix[k]) {
          if (y = toVal(mix[k])) {
            str && (str += ' ');
            str += y;
          }
        }
      }
    } else {
      for (k in mix) {
        if (mix[k]) {
          str && (str += ' ');
          str += k;
        }
      }
    }
  }
  return str;
}

function cx() {
  var i=0, tmp, x, str='';
  while (i < arguments.length) {
    if (tmp = arguments[i++]) {
      if (x = toVal(tmp)) {
        str && (str += ' ');
        str += x;
      }
    }
  }
  return str;
}
cx("boo", "oh no", "lol", "", "OH NO");

filter-and-join.js

function cx(...strings) {
  return strings.filter(Boolean).join(' ');
}
cx("boo", "oh no", "lol", "", "OH NO");

simple-join.js

function cx(...strings) {
  return strings.join(' ');
}
cx("boo", "oh no", "lol", "", "OH NO");