CODEWITHSUNDEEP
javascripthtml
user1275375
user1275375

Reputation: 1391

Can we create log files using javascript

Instead fo displaying in alert box I want to direct my output from javascript to a log file. Is there any method for doing it. If so please explain it with an example.

Upvotes: 5

Views: 14990

Answers (4)

Peter
Peter

Reputation: 4701

Actually there is a way to do it but it is only available on Google Chrome and mostly for HTML5 applications packaged as extensions. There are plans to make it available in wider distributions but not quite there yet. It is called the FileSystem API. Here is an example I was playing with a while ago -

// test HTML5 file system API

function onInitFs(fs){
    console.log("Opened file system " + fs.name);
}

function errorHandler(){
    var msg = '';

    switch(e.code){
        case FileError.QUOTA_EXCEEDED_ERR:
            msg = 'QUOTA_EXCEEDED_ERR';
            break;
        case FileError.NOT_FOUND_ERR:
            msg = 'NOT_FOUND_ERR';
            break;
        case FileError.SECURITY_ERR:
            msg = 'SECURITY_ERR';
            break;
        case FileError.INVALID_STATE_ERR:
            msg = 'INVALID_STATE_ERR';
            break;
        default:
            msg = 'Unknown Error';
            break;
    };

    console.log('Error: ' + msg);
}

window.requestFileSystem(
    window.TEMPORARY,
    5*1024*1024 /*5MB*/,
    onInitFs,
    errorHandler
);

// create empty file called log.txt
// throws an error e is not defined
function onInitFs(fs){
    fs.root.getFile(
        'log.txt', 
        {
            create: true, 
            exclusive: true
        },
        function(fileEntry){
            console.log('fileEntry.isFile = ' + fileEntry.isFile);
            console.log('fileEntry.name = ' + fileEntry.name);
            console.log('fileEntry.fullPath ' + fileEntry.fullPath);
        },
        errorHandler
    );
}

function errorHandler(){
    var msg = '';

    switch(e.code){
        case FileError.QUOTA_EXCEEDED_ERR:
            msg = 'QUOTA_EXCEEDED_ERR';
            break;
        case FileError.NOT_FOUND_ERR:
            msg = 'NOT_FOUND_ERR';
            break;
        case FileError.SECURITY_ERR:
            msg = 'SECURITY_ERR';
            break;
        case FileError.INVALID_STATE_ERR:
            msg = 'INVALID_STATE_ERR';
            break;
        default:
            msg = 'Unknown Error';
            break;
    };

    console.log('Error: ' + msg);
}

window.requestFileSystem(
    window.TEMPORARY, 
    5*1024*1024,
    onInitFs,
    errorHandler
);

// simple debugging
window.requestFileSystem(
    window.TEMPORARY,
    5*1024*1024,
    function(fs){
        console.dir(fs.root);
        fs.root.getFile('log.txt');
    },
    function(error){
        console.dir(error);
    }
);

Upvotes: 2

user1289347
user1289347

Reputation: 2407

Yes, using the google chrome browser hit the f12 key, and click on the console button. Then use 

console.log(your code);

you can log objects, arrays, strings ,variables. Much more useful than alerts.

Also in firefox the firebug plugin is quite useful. Has similar functionality, and adds the inspect element function that google chrome has built in.

EDIT: Ok, based on your comment, you cannot just write to their file system. The browser will not let you. If you want something unobtrusive try something like a classy modal window or overlay, something that is optional for the user to interact with rather than the annoying alerts and confirms. You could even add something like this http://davidwalsh.name/dw-content/top-bar-opacity.php

Upvotes: 5

Steve
Steve

Reputation: 8640

You could always send an AJAX call back to the server and track error messages there.

Upvotes: 2

Greg Hewgill
Greg Hewgill

Reputation: 993085

Most browsers support the window.console object from the Console API:

console.log("Hello world");

Upvotes: 3

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