JavaScript Utilility functions

utils.js

// Test for numeric value.
function isNumeric(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}

/**
 * @param {Event} e
 * @see <https://www.w3.org/TR/uievents/#interface-keyboardevent>
 * All browsers (IE11, Chrome, FF, etc.) support event.key.
 * event.keyCode, charCode and event.which are deprecated.
 */
function isModifierKey(e) {
  let key = e.key; // key value of the key pressed.
  return (e.ctrlKey || e.metaKey || e.shiftKey || e.altKey ||
          key == "Backspace" || key == "Tab" || 
          key == "Delete" || key == "Enter");
}