[使用quaggajs的功能掃描barcode.在安卓系統上是正常。IOS也可以運行。]
[不過在縮放(zoom)與閃光燈功能(torch)方面，IOS系統卻無效果，請求各位幫忙。]

     // 啟動掃描
        Quagga.init({
          inputStream : {
            name : "Live",
            type : "LiveStream",
            target: document.querySelector('#canvanCode'),
            constraints: {
              width: p_width,
              height: p_height,
              facingMode:"environment"
            }
          },
          frequency:20,
            decoder : {
              readers : ["ean_reader"],
              halfSample :true,
              patchSize:"x-large",
              // patchSize:"medium",
              // patchSize:"x-small",
              debug: {
                drawBoundingBox: false,
                showFrequency: false,
                drawScanline: false,
                showPattern: false
              },
              multiple: false
            }
          }, function(err) {
              if (err) {
                console.log(err);
                return
              }
              var track = Quagga.CameraAccess.getActiveTrack();
              track.applyConstraints({advanced: [{zoom: 4}]});
              console.log("Initialization finished. Ready to start");
              Quagga.start();
              Quagga.onDetected(function(data){

                console.log(data);

                //計次(相同累積次數)
                  if(code_old_name==data.codeResult.code){
                    code_old_number=code_old_number+1;
                  }
                  else{
                    code_old_number=0;
                    code_old_name=data.codeResult.code;
                  }

	               //重複3次相同
                  if(code_old_number>=1){
                    code_old_number=0;
                    val=data.codeResult.code;
                    Quagga.stop();
                    document.getElementById('key_isbn_number').value=val;
                    code_old_name=Math.floor(Math.random()*50);

                    // 傳值
                      window.opener.document.getElementById('key_isbn_number').value=val;
                      window.opener.show_call();
                      window.close();
                  }
              })

        });