How do I make a Chrome extension that opens a web form and auto-populates specific input fields?

Question

I am new to using chrome extensions and i have a run into a little problem with setting up a chrome extension. I want the extension to read specific values from a web page and then open up a specific page (form with a number of input fields) from a flask application that I have built in a new tab and then use the values that have been scraped to populate specific fields in the page from my flask app.

I have managed to get the extension to generate a new tab and to load the page from my flask app but I am unable to get the fields to populate. It would seem that the page gets loaded before the fields are populated. I have pasted some code to show you how far I have got. The other issue is that I am using the code parameter from executeScripts to perform the populating action but I don't seem to be able to pass arguments into the code string (I suspect this is not the way to do this but I am working off an answer that I have found very helpful up to this point from here https://stackoverflow.com/a/41094570/1977981 Any help would be much appreciated.

manifest.json

{
  "manifest_version": 2,
  "name": "My Cool Extension",
  "version": "0.1",
  "permissions": [
  "http://localhost:****/lesson/1/note/new/"
    ],
  "content_scripts": [
  {
  "matches": [
    "<all_urls>"
    ],
  "js": ["jquery-3.2.1.min.js", "content.js"]
  }
 ],
  "browser_action": {
  "default_icon": "icon.png"
 },
  "background": {
  "scripts": ["jquery-3.2.1.min.js", "background.js"]
 }
}

content.js

// Triggered by sendMessage function in background.js
chrome.runtime.onMessage.addListener(
    function(request, sender, sendResponse) {
        // listening for request message
        if( request.message === "clicked_browser_action" ) {
            //  Retrieve Lesson title from current tab
            var lesson = $('._tabbed-sidebar--title--1Dx5w').find('span').text()

            // output this value to the console
            console.log(lesson);

            // Send a single message to the event listener in your extension i.e. background.js

          chrome.runtime.sendMessage({"message": "open_new_tab", "lesson": lesson})
    }
  }
);

background.js

// Called when the user clicks on the browser action icon.
chrome.browserAction.onClicked.addListener(function(tab) {

    // Send a message to the active tab
    chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {

    // take the current tab shown in the window
    var activeTab = tabs[0];

    // Send a message to contents.js - this message is being listened for by contents.js and the runtime.onMessage event is fired in content.js script
    chrome.tabs.sendMessage(activeTab.id, {"message": "clicked_browser_action"});

      });
});

// listening for "open_new_tab" message from content.js
chrome.runtime.onMessage.addListener(
    function(request, sender, sendResponse) {
        if( request.message === "open_new_tab" ) {

            // create new tab but do not activate the tab yet
            chrome.tabs.create({"url": "http://localhost:5000/lesson/1/note/new/", active: false }, function(tab){


                // load jquery functionality execute script
                chrome.tabs.executeScript(tab.id, {file: "jquery-3.2.1.min.js"}, function(results){

                    chrome.tabs.executeScript(tab.id,{code:`
                       (function(arguments){
                           var count = 100; //Only try 100 times
                           function autofill(){
                               var lesson = $('.lesson_subsection');
                               console.log(lesson);
                               if(lesson){
                                   lesson.value = arguments[0].lesson;
                               } else {
                                   if(count-- > 0 ){
                                   //The elements we need don't exist yet, wait a bit to try again.
                                       setTimeout(autofill,250);
                                    }
                               }
                           }
                           autofill();
                       }, request)();
                   `}, function(results){

                    chrome.tabs.update(tab.id,{active:true});
                          }); //END OF second executeScript function
}); // END OF first executeScript function

    } // END OF chrome.tabs.create anonymous function
    ); // END OF chrome.tabs.create
} // END OF if( request.message === "open_new_tab" ) {
}); // END OF addListener anonymous function

The injected code is a content script, it runs in a different page, hence it cannot see `request`. You need to add it explicitly to the code string by concatenating with JSON.stringify as shown at the end of the accepted answer in [Insert code into the page context using a content script](//stackoverflow.com/a/9517879) — wOxxOm, Sep 04 '17 at 17:34
Also, `}, request)();` seems a typo. You probably meant `})(request);` - but see my comment above. — wOxxOm, Sep 04 '17 at 17:36

user1977981 · Answer 1 · 2017-09-06T09:18:50.523

Thank you @wOxxOm your comments were very helpful. I was able to use JSON.stringify to load the arguments in to the injected code string. I also had to load the input element from my form using document.getElementsByClassName() instead of using the jquery version of the object. This also meant i didn't have to load the jquery library see line shown below

var less = document.getElementsByClassName('lesson_subsection')[0];

Now my chrome.runtime.onMessage.addListener function in my background.js script is as follows:

// See content.js function
chrome.runtime.onMessage.addListener(
    function(request, sender, sendResponse) {
        if( request.message === "open_new_tab" ) {
            chrome.tabs.create({"url": "http://localhost:5000/lesson/1/note/new/", active: false }, function(tab){
            console.log('Attempting to inject script into tab:',tab);
            chrome.tabs.executeScript(tab.id,{code:`
                (function(argument){
                     var count = 100; //Only try 100 times
                     function autofill(){
                     var less = document.getElementsByClassName('lesson_subsection')[0];
                     if(less){
                         less.value = argument;
                     } else {
                           if(count-- > 0 ){
                               //The elements we need don't exist yet, wait a bit to try again.
                               setTimeout(autofill,250);
                    }
                }
            }
            autofill();
        })(` + JSON.stringify(request.lesson) + `);
    `}, function(results){
            // chrome.tabs.sendMessage(tab.id, {"message": "need to update tab", "tab": tab.id});
            chrome.tabs.update(tab.id, { active: true });

    }); //END OF executeScript function

    } // END OF chrome.tabs.create anonymous function
    ); // END OF chrome.tabs.create
  } // END OF if( request.message === "open_new_tab" ) {
}); // END OF addListener anonymous function

How do I make a Chrome extension that opens a web form and auto-populates specific input fields?

1 Answers1