CODEWITHSUNDEEP
javascriptajaxfirefox-addoncontent-scriptfirefox-addon-webextensions
Gladclef
Gladclef

Reputation: 709

XMLHttpRequest Status 0 for Firefox 49.0.2 Add On

There is a XMLHttpRequest in the content script of my Firefox WebExtensions add on. Q: why is the status of this request is always 0?

This is the JavaScript code making the request:

var query = "http://api.wolframalpha.com/v2/query?appid=[MY-APP-ID]&includepodid=Comparison&scanner=Unit&format=plaintext&input=1%20lm";
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function()
{
    console.log("onreadystatechange");
    console.log(this);
    if (this.readyState == 4 && this.status == 200)
    {
        onSuccess(this.responseText);
    }
};
xhttp.open("GET", query, true);
xhttp.send();

If I print out the results of the request for each onreadystatechange call, I get:

XMLHttpRequest { onreadystatechange: makeWolframRequest/xhttp.onreadystatechange(),
    readyState: 1, timeout: 0, withCredentials: false, upload: XMLHttpRequestUpload,
    responseURL: "", status: 0, statusText: "", responseType: "", response: "" }
XMLHttpRequest { onreadystatechange: makeWolframRequest/xhttp.onreadystatechange(),
    readyState: 2, timeout: 0, withCredentials: false, upload: XMLHttpRequestUpload,
    responseURL: "", status: 0, statusText: "", responseType: "", response: "" }
XMLHttpRequest { onreadystatechange: makeWolframRequest/xhttp.onreadystatechange(),
    readyState: 4, timeout: 0, withCredentials: false, upload: XMLHttpRequestUpload,
    responseURL: "", status: 0, statusText: "", responseType: "", response: "" }

Things I checked:

Upvotes: 3

Views: 771

Answers (1)

Gladclef
Gladclef

Reputation: 709

In this case it was a CORS issue. I had to add this secret sauce to my manifest.json file:

"permissions": [
    "http://api.wolframalpha.com/*"
]

More information here: https://developer.mozilla.org/en-US/Add-ons/WebExtensions/manifest.json/permissions

Much thanks to @adeneo for insisting I keep looking at CORS issues.

Upvotes: 1

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