一起看看js获取扫码枪输入数据的方法

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。

 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 = &#39;&#39;;
     lastCode = &#39;&#39;;
     lastTime = &#39;&#39;;
     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

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 = {&#39;48&#39;:48,&#39;49&#39;:49,&#39;50&#39;:50,&#39;51&#39;:51,&#39;52&#39;:52,&#39;53&#39;:53,&#39;54&#39;:54,&#39;55&#39;:55,&#39;56&#39;:56,&#39;57&#39;:57,
			 &#39;96&#39;:48,&#39;97&#39;:49,&#39;98&#39;:50,&#39;99&#39;:51,&#39;100&#39;:52,&#39;101&#39;:53,&#39;102&#39;:54,&#39;103&#39;:55,&#39;104&#39;:56,&#39;105&#39;: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(&#39;A类条码:&#39; + code);
      } else if (code.length == 23) {
				this.$message(&#39;B类条码:&#39; + code);
      } else if (code.length == 0) {
				this.$message(&#39;请输入条码&#39;);
      } else{
      	this.$message(&#39;条码不合法：&#39; + code);
      }
      //键入回车务必清空code值
    	this.code = &#39;&#39;
    	return false;
    }
  }
}

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