Reading first line of a text file in javascript

Question

Let's say I have a text file on my web server under /today/changelog-en.txt which stores information about updates to my website. Each section starts with a version number, then a list of the changes.

Because of this, the first line of the file always contains the latest version number, which I'd like to read out using plain JavaScript (no jQuery). Is this possible, and if yes, how?

is the file available externally? ie: can it be reached via an XHR/AJAX request? — Christopher, Sep 01 '12 at 12:31
Would you hypothetically be able to provide a url that would result in the txt file in question? If so I can show you what code to write to achieve the results you're looking for. — Christopher, Sep 01 '12 at 12:36
cool, then we can just make a XHR request, will post an answer now. — Christopher, Sep 01 '12 at 12:37
@TinaCGHoehr I always get jQery answers which I don't feel like learning now, that's why it's there. — SeinopSys, Sep 01 '12 at 12:47

score 7 · Accepted Answer · edited Feb 03 '16 at 13:29

7

This should be simple enough using XHR. Something like this would work fine for you:

var XHR = new XMLHttpRequest();
XHR.open("GET", "/today/changelog-en.txt", true);
XHR.send();
XHR.onload = function (){
    console.log( XHR.responseText.slice(0, XHR.responseText.indexOf("\n")) );
};

edited Feb 03 '16 at 13:29

SeinopSys

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answered Sep 01 '12 at 12:46

Some Guy

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And how do I make this working with an HTML file? Edit: Now makes sense :D – SeinopSys Sep 01 '12 at 12:47
@DJDavid98 Simply put it in the `script` tags. Where you see `console.log`, put some function that uses the version number. – Some Guy Sep 01 '12 at 12:48
Yeah, I know, only that 1 line was missong from the top. Works great! – SeinopSys Sep 01 '12 at 12:51
@DJDavid98 Yeah, sorry about that. – Some Guy Sep 01 '12 at 12:52

score 2 · Answer 2 · edited Feb 03 '16 at 13:30

2

So seeing as the txt file is externally available ie: corresponds to a URL, we can do an XHR/AJAX request to get the data. Note without jQuery, so we'll be writing slightly more verbose vanilla JavaScript.

var xmlHttp;

function GetData( url, callback ) {

    xmlHttp = new XMLHttpRequest(); 
    xmlHttp.onreadystatechange = callback;
    xmlHttp.open( "GET", url, true );
    xmlHttp.send( null );
}

GetData( "/today/changelog-en.txt" , function() {

    if ( xmlHttp.readyState == 4 && xmlHttp.status == 200 {

        var result = xmlHttp.responseText;
        var allLines = result.split("\n");

        // do what you want with the result 
        // ie: split lines and show the first line

        var lineOne = allLines[0];

    } else {
        // handle the error
    }
});

edited Feb 03 '16 at 13:30

SeinopSys

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answered Sep 01 '12 at 12:51

Christopher

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Sorry, but Amaan's version is much more compact. That does not mean yours is bad, it's just that I like to do it the simpiest way possible. – SeinopSys Sep 01 '12 at 12:53
well its up to you, though, mine has the ability to re-use the code, and handle errors responsibly. – Christopher Sep 01 '12 at 12:54

Reading first line of a text file in javascript

2 Answers2

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