Firebase上的“未捕获的TypeError：未定义不是函数”错误

Question

I'm very new to web development and I have an error with firebase error.

I'm using Firebase and jQuery to make an web application which recognizes voice and translates it to text. (Speech-to-Text, STT)

I have to push the STT results in realtime so that all clients could see the text.

However, the problem occurs in this event listener:

finalSTTField.click(function (e) {
        var message = finalSTTField.val();
        sttRef.push({ text: message } );
    });

As a result of STT, a string is in the finalSTTField which is declared like below:

var finalSTTField = $('#final_span');

And I want to push the string by using the firebase:

var sttRef = new Firebase('https://sizzling-torch-2935.firebaseio.com/');

and

<div class="sttResultContainer">
    <ul id="sttMessages"></ul>
</div>

with

var sttResults = $('#sttMessages');

sttRef.limitToLast(10).on('child_added', function (snapshot) {
        var data = snapshot.val();
        var sttText = data.value();

        var messageElement = $("<li>");
        messageElement.text(sttText);
        sttResults.append(messageElement);
        sttResults[0].scrollTop = sttResults[0].scrollHeight;
    });

But nothing shows in sttResults.

The error message on chrome browser is: firebase.js:26 Uncaught TypeError: undefined is not a function

Error count increases every time the click event occurs. (Strangely, the count starts at 10)

The first STT transcripts are showing well in the #final_span span. But I have to push the string in #final_span in realtime...

Somebody help me please! It's my first web application...

Full source code is here: full source in JSFiddle

Answer 1

This line is wrong:

var sttText = data.value();

After you call val() on the snapshot to get the value, you get a JSON object. No methods are defined on that object. Your text is instead in a child property, so you can get it like:

var data = snapshot.val();
var sttText = data.text;

Note that it is fairly easy to find such a problem, if you put a console.log statement after extracting the data:

var data = snapshot.val();
console.log(data);

This is a very common troubleshooting technique. In your fiddle it prints:

Object {text: ""}