numberOnly.js

/**
 * Avoid non-numeric characters on input text
 */
numberOnly(event) {
  const value = event.target.value;
  const lastChar = value.length > 0 ? Number(value[value.length - 1]) : 0 ;
  const isNaN = char => char !== char;
  if ( isNaN(lastChar) ) {
    return false;
  }
}