decode event execute twice

[marshall-li]

I am using vue-barcode-reader in vue2.0.vue-barcode-reader version is 0.0.3

<StreamBarcodeReader @decode="onDecode" @loaded="onLoaded">
onDecode(decodedString) {
this.$refs.audio.play()
alert(decodedString);
this.scanSuccess(decodedString)
this.showScan = false
},

I found the decode event execute twice. because the alert execute twice. If i want this event execute once. what can i do.