src/KeyboardPrefixSelectionMixin.js
function handlePlainCharacter(element, char) {
  const prefix = element[typedPrefixKey] || '';
  element[typedPrefixKey] = prefix + char;
  element.selectItemWithTextPrefix(element[typedPrefixKey]);
  setPrefixTimeout(element);
}
function handlePlainCharacter(element, char) {
  const prefix = element[typedPrefixKey] || '';
  element[typedPrefixKey] = prefix + char;
  element.selectItemWithTextPrefix(element[typedPrefixKey]);
  setPrefixTimeout(element);
}
function handlePlainCharacter ( element , char ) { const prefix = element [ typedPrefixKey ] || '' ; element [ typedPrefixKey ] = prefix + char ; element . selectItemWithTextPrefix ( element [ typedPrefixKey ] ) ; setPrefixTimeout ( element ) ; }
Add a plain character to the prefix.
Add a plain character to the prefix .