JS 如何获取扫码枪输入数据

朱雀 2020-07-01 16:06 746阅读 0赞

# JS 如何获取扫码枪输入数据

1、扫码枪相当于**键盘输入设备**，输入一连串数字后加一个**enter**键。但在实际开发中需要区分是扫描枪输入还是键盘用户输入，区别在于扫码枪输入很快。

```js
let code = '';
  let lastTime, nextTime;
  let lastCode, nextCode;
  window.document.onkeypress = (e) => {
   if (window.event) { // IE
    nextCode = e.keyCode;
   } else if (e.which) { // Netscape/Firefox/Opera
    nextCode = e.which;
   }
   if (nextCode === 13) {
    if (code.length < 3) return; // 手动输入的时间不会让code的长度大于2，所以这里只会对扫码枪有
 
    console.log(code); // 获取到扫码枪输入的内容，做别的操作
 
    code = '';
    lastCode = '';
    lastTime = '';
    return;
   }
   nextTime = new Date().getTime();
   if (!lastTime && !lastCode) {
    code += e.key;
   }
 
   if (lastCode && lastTime && nextTime - lastTime > 30) { // 当扫码前有keypress事件时,防止首字缺失
    code = e.key;
   } else if (lastCode && lastTime) {
    code += e.key;
   }
   lastCode = nextCode;
   lastTime = nextTime;
  }
```

**PS：下面看下js获取USB扫码枪数据的代码**

**前言**

找了很多相关的教程不太好用，汲取各家之长总结精简了一下

**原理**

1. 扫码枪扫描到的条形码每一位会触发一次onkeydown事件
2. 比如扫描条码位‘1234567890'的条形码，会连续执行10次onkeydown事件
3. 条码扫描到最后一位，会直接触发Enter

需要引入jQuery，我这里用的是vue

```js
window.onload = (e)=> {
  document.onkeydown = (e)=> {
    let nextCode,nextTime = '';
    let lastTime = this.lastTime;
    let code = this.code;
    if (window.event) {// IE
      nextCode = e.keyCode
    } else if (e.which) {// Netscape/Firefox/Opera
      nextCode = e.which
    }
    nextTime = new Date().getTime();
    //字母上方 数字键0-9 对应键码值 48-57; 数字键盘 数字键0-9 对应键码值 96-105
    if((nextCode>=48&&nextCode<=57) || (nextCode>=96&&nextCode<=105)){
        let codes = {'48':48,'49':49,'50':50,'51':51,'52':52,'53':53,'54':54,'55':55,'56':56,'57':57,
             '96':48,'97':49,'98':50,'99':51,'100':52,'101':53,'102':54,'103':55,'104':56,'105':57
            };
            nextCode = codes[nextCode];
            nextTime = new Date().getTime();
    }
    // 第二次输入延迟两秒，删除之前的数据重新计算
    if(nextTime && lastTime && nextTime-lastTime>2000){
            code = String.fromCharCode(nextCode);
    }else{
        code += String.fromCharCode(nextCode)
    }
    // 保存数据
    this.nextCode = nextCode;
    this.lastTime = nextTime;
    this.code = code;
    // 键入Enter
    if(e.which == 13) {
      // 判断 code 长度（这里就获取到条码值了，以下业务自由发挥）
        code = $.trim(code)
      if (code.length == 13) {
        this.$message('A类条码:' + code);
      } else if (code.length == 23) {
                this.$message('B类条码:' + code);
      } else if (code.length == 0) {
                this.$message('请输入条码');
      } else{
        this.$message('条码不合法：' + code);
      }
      //键入回车务必清空code值
        this.code = ''
        return false;
    }
  }
}
```