How to set a value to a file input in HTML?

Question

How can I set the value of this?

Answer 1

As everyone else here has stated: You cannot upload a file automatically with JavaScript.

HOWEVER! If you have access to the information you want to send in your code (i.e., not passwords.txt), then you can upload it as a blob-type, and then treat it as a file.

What the server will end up seeing will be indistinguishable from someone actually setting the value of . The trick, ultimately, is to begin a new XMLHttpRequest() with the server...

function uploadFile (data) {
        // define data and connections
    var blob = new Blob([JSON.stringify(data)]);
    var url = URL.createObjectURL(blob);
    var xhr = new XMLHttpRequest();
    xhr.open('POST', 'myForm.php', true);

        // define new form
    var formData = new FormData();
    formData.append('someUploadIdentifier', blob, 'someFileName.json');

        // action after uploading happens
    xhr.onload = function(e) {
        console.log("File uploading completed!");
    };

        // do the uploading
    console.log("File uploading started!");
    xhr.send(formData);
}

    // This data/text below is local to the JS script, so we are allowed to send it!
uploadFile({'hello!':'how are you?'});

So, what could you possibly use this for? I use it for uploading HTML5 canvas elements as jpg's. This saves the user the trouble of having to open a file input element, only to select the local, cached image that they just resized, modified, etc.. But it should work for any file type.