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+--- Thread: returning a message from a background script (/showthread.php?tid=70361)
returning a message from a background script - richb201 - 03-30-2018
I have managed to get a response back from the server back to the background script in my Chrome extension that it is communicating with. Now I need to get a message back to the popup so I can repopulate a table. Here is the code that gets the response back from the server in a function called send_to_backend(). This function is being called when the within and onload when the readyState=200 is satisfied.
Code:
function send_to_backend()
{
myArray["email"]=jsonResponse["email"];
var json = JSON.stringify(myArray);
var url = 'http://localhost/Subit_backend/register';
var xhr = new XMLHttpRequest();
xhr.onerror = function() { alert('error'); };
xhr.open('POST', url, true);
xhr.setRequestHeader("Content-type", "application/json");
xhr.setRequestHeader("X-Requested-With",'xmlhttprequest');
xhr.onload = function () { //response will go here
if(xhr.status === 200) {
var jsonResponse = JSON.parse(xhr.responseText);
// Log the whole json object
console.log(jsonResponse);
// Access 'success' from the object
console.log(jsonResponse.success);
sendResponse({response: jsonResponse.success}); <<< here
//return(jsonResponse);
}
// Request finished. Do processing here.
};- "response is not defined"
- stack:"ReferenceError: response is not defined↵ at eval (eval at xhr.onload (chrome-extension://bdjgnodlhfmhghjhbkkkaaammfocdpib/background.js:108:5), <anonymous>:1:1)↵ at XMLHttpRequest.xhr.onload (chrome-extension://bdjgnodlhfmhghjhbkkkaaammfocdpib/background.js:108:5)"
RE: returning a message from a background script - richb201 - 03-31-2018
I did some more searching and think I understand the issue better.
1. My popup script sends a message to my background script to get some info xhr from the server.
2. My background script gets a token asynchronously to check for authentication.
3. When I get an onload and readyState=200 (ok) from the token request I call a function called send_to_backend() which gets the data I need from my server asynchronously. Send_to Backend is not called asynchronously, but inside it it has an asynch call to the server.
4. My call to Send_to_backend() returns immediately to the call within the anon onMessage function, before this is before the asynch response from the server is ready.
5. I immediately send the "uncooked response" back to the popup script.
6. If instead i try to send the message back to the popup from within send_to_backend, sendResponse is not defined. I guess this is because I am not within the onMessage function?
The reason I created the send_to_backend function was to get out of "callback hell" and to make the code readable. But send_to_backend is not a callback itself, it is a function, and of course, is not blocking either.
Any ideas on how to deal with this? If I could just send the message from send_to_backend() to the popup script things seem to be working OK.
RE: returning a message from a background script - richb201 - 03-31-2018
Well ,thinking about it, perhaps I should break it into two steps:
1) popup send message to background script to authenticate user
2) background script catches "authenticate" string and authenticates and sends either an OK or a false back to popup.
3) if OK, the popup script sends a message to the background script to "login"
4) background script sends a XMLHttpRequest to the server which responds with the payload.
5) background script sends a message back to the popup script with the payload.
Maybe this makes more sense, rather than getting stuck in callback hell. Any flaws in this plan?