File reader Javascript

Question

currently i am choosing a file and converting to base64 string and displaying in html page.see the below code. But i want in such a way that while loading the function it will automatically fetch the file from the location where the image saved and convert to base64 and display. I just want to skip the manual way of choosing..please help

<html>
<body>
Choose File: <input id="imageToLoad" type="file" onchange="displayImage();" />
<p>Image encoded</p>
<textarea id="base64TextArea" style="width:550;height:240" ></textarea>
<img id="myImg" width="218" height="300"  src="" />
<script type="text/javascript">

function displayImage()
{
    var filesSelected = document.getElementById("imageToLoad").files;


    if (filesSelected.length > 0)
    {
        var fileToLoad = filesSelected[0];

        var fileReader = new FileReader();

        fileReader.onload = function(fileLoadedEvent) 
        {



            base64TextArea.innerHTML = fileLoadedEvent.target.result;
            document.getElementById("myImg").src = fileLoadedEvent.target.result;
        };

        fileReader.readAsDataURL(fileToLoad);
    }
}

</script>

</body>
</html>

Carcigenicate · Accepted Answer · 2016-08-11 16:40:33Z

2

You can't fetch arbitrary files on a client's computer with JS. Using most browsers, the client must manually choose a file to be processed by the script.

If you think about it, it would be a major security flaw if any website could access any file on your computer.

edited Aug 11, 2016 at 16:40

answered Aug 11, 2016 at 16:37

Carcigenicate

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9 Comments

MrBizle Over a year ago

Further to that, it's a XSS nightmare

Pierpaolo Cira Over a year ago

Yes, if a browser is allowed to arbitrary access to filesystem resources, then there is a strong security issue!!!

Katana314 Over a year ago

...and this isn't what the script is doing? They have an <input type="file"> and onchange. This is very possible in HTML5.

Carcigenicate Over a year ago

@Katana314 The user needs to pick a file using a dialog in that case. The script can't pick a certain file and open it without manual intervention from the client.

Katana314 Over a year ago

@Carcigenicate ...which, again, is HAPPENING in this example. They have a visible file input, from which the user picks an image, and once picked the script runs. OP does not plan for this to be fully automated. You need to pay more attention to the question.

|

Katana314 · Accepted Answer · 2016-08-11 16:51:57Z

-1

I'm not sure why Base64 is an important aspect here. Please give some details if converting the image to text is a specific requirement of your needs, but if you only want to display and reference the image, you can start with this:

if (filesSelected.length > 0)
    {
        var fileToLoad = filesSelected[0];

        document.getElementById("myImg").src = URL.createObjectURL(fileToLoad);
    }

This will use an "object URL" which is a shorthand way of referring to a file that has been drag/dropped, or picked from an <input>

answered Aug 11, 2016 at 16:51

Katana314

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4 Comments

Jayesh Over a year ago

I have an html report generating in my application while running some tests, and also some screen prints will be taken during the tests. I just want to upload only this html file to remote server with embedded image init.

Katana314 Over a year ago

@jayesh You want to upload an HTML file? Where is this upload happening? A much smoother way of doing it would be to embed the image's data directly into that HTML using a data URL, or place it in a hosting location next to the HTML. This sounds like the way your reports are made is very relevant to the issue.

Jayesh Over a year ago

yes I want to upload only the html file not the image files, images I can embed in html page..these images are in specific location in my application, how do I get the image files in jS methods so that i can convert to bse64 string and embed

Katana314 Over a year ago

@jayesh I don't follow - it seems like you already have all of that. What exactly are you trying to embed in your HTML upload; a url like "images/photos/3.jpg", or a data URL, like the one generated by this HTML page? If your images are hosted in your application, you can easily reference them by URL without even working with FileReader. If you can embed the data-URL in the <img src=" tag, that should also work. But I'm unclear how this image you want to automatically show is coming in.

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