js怎么区分扫码枪输入还是键盘输入

1、var code = '';

var lastTime, nextTime;

var lastCode, nextCode;

 keyboardEvent (keyEvent) {

    nextCode = keyEvent.keyCode;

    nextTime = new Date ().getTime ();

    if (lastCode != null && lastTime != null && nextTime - lastTime <= 30) {

      code += lastCode - 7;

    } else if (

      lastCode != null &&

      lastTime != null &&

      nextTime - lastTime > 100

    ) {

      code = '';

    }

    lastCode = nextCode;

    lastTime = nextTime;

    if (keyEvent.keyCode == 66) {

   console.log(code)

    }

  }