get event char code

/**
 * `charCode` represents the actual "character code" and is safe to use with
 * `String.fromCharCode`. As such, only keys that correspond to printable
 * characters produce a valid `charCode`, the only exception to this is Enter.
 *
 * `charCode` 表示实际的“字符编码”，可安全用于 `String.fromCharCode`。因此，只有对应可打印字符的按键才会生成有效的 `charCode`，唯一的例外是回车键。
 *
 * The Tab-key is considered non-printable and does not have a `charCode`,
 * presumably because it does not produce a tab-character in browsers.
 *
 * Tab键被认为是不可打印的，并且没有 `charCode`，* 大概是因为它在浏览器中不会产生制表符。
 *
 * @param {object} nativeEvent Native browser event.
 *                  nativeEvent 原生浏览器事件。
 * @return {number} Normalized `charCode` property.
 *                  标准化的 `charCode` 属性。
 */
function getEventCharCode(nativeEvent: KeyboardEvent): number {
  let charCode;
  const keyCode = nativeEvent.keyCode;

  if ('charCode' in nativeEvent) {
    charCode = nativeEvent.charCode;

    // FF does not set `charCode` for the Enter-key, check against `keyCode`.
    // FF 不会为回车键设置 `charCode`，请检查 `keyCode`。
    if (charCode === 0 && keyCode === 13) {
      charCode = 13;
    }
  } else {
    // IE8 does not implement `charCode`, but `keyCode` has the correct value.
    // IE8 不支持 `charCode`，但 `keyCode` 有正确的值。
    charCode = keyCode;
  }

  // IE and Edge (on Windows) and Chrome / Safari (on Windows and Linux)
  // report Enter as charCode 10 when ctrl is pressed.
  // IE 和 Edge（在 Windows 上）以及 Chrome / Safari（在 Windows 和 Linux 上）
  // 当按下 ctrl 时，报告 Enter 为 charCode 10。
  if (charCode === 10) {
    charCode = 13;
  }

  // Some non-printable keys are reported in `charCode`/`keyCode`, discard them.
  // Must not discard the (non-)printable Enter-key.
  // 一些不可打印的按键会在 `charCode`/`keyCode` 中被报告，丢弃它们。
  // 不能丢弃（不可打印的）回车键。
  if (charCode >= 32 || charCode === 13) {
    return charCode;
  }

  return 0;
}

export default getEventCharCode;