代码每个事件执行多次：多次下载

Question

我想从内容脚本中下载JSON对象。首先，当我请求下载时，它下载一个文件，但在第二个请求时，它下载两个文件;在第三次请求时，下载了三个文件，等等。

Background.js

chrome.browserAction.onClicked.addListener(function (tab) {
    download();
    chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
        //Alert the message
        console.log(request);
        chrome.downloads.download({
            url: request.method,
            filename: request.name
        }, function (downloadId) {

        });
        //You have to choose which part of the response you want to display 
        //  ie. request.method
        //alert('The message from the content script: ' + request.method);
        //Construct & send a response
        sendResponse({
            response: "Message received"
        });
    });
});

function download() {
    chrome.tabs.executeScript(null, {
        file: "jquery.js"
    }, function () {
        chrome.tabs.executeScript(null, {
            file: "content_script.js"
        });
    });
}

内容脚本

function sendMessage(url, filename) {
    //Construct & send message
    chrome.runtime.sendMessage({
        method: url,
        name: filename
    }, function (response) {
        //Alert the message
        //You have to choose which part of the response you want to display 
        //  ie.  response.response

        //alert("The response from the background page: " + response.response);
    });
}
var json = JSON.stringify(ticket);
var blob = new Blob([json], {
    type: "application/json"
});
var url = URL.createObjectURL(blob);
var a = document.createElement('a');
a.download = "backup.json";
a.href = url;
a.textContent = "Download backup.json";
var container = document.getElementById('ticketDetail');
//container.appendChild(a);
var fName = ticket.date.replace(".", "_")
sendMessage(url, fName.replace(".", "_") + ".json");

Answer 1

与这种问题模式的情况一样，问题是您要向事件添加多个匿名侦听器。具体来说，每次单击chrome.runtime.onMessage时，您都会添加另一个action_button侦听器。您只需要添加一次侦听器。

对此的简单解决方案是只添加chrome.runtime.onMessage一次：

chrome.browserAction.onClicked.addListener(function (tab) {
    download();
});

chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
    //Alert the message
    console.log(request);
    chrome.downloads.download({
        url: request.method,
        filename: request.name
    }, function (downloadId) {
    });
    //You have to choose which part of the response you want to display 
    //  ie. request.method
    //alert('The message from the content script: ' + request.method);
    //Construct & send a response
    sendResponse({
        response: "Message received"
    });
});

function download() {
    chrome.tabs.executeScript(null, {
        file: "jquery.js"
    }, function () {
        chrome.tabs.executeScript(null, {
            file: "content_script.js"
        });
    });
}