Upload File as String to JavaScript Variable

Question

Is there any way for a client to upload a file in an HTML form (e.g. .txt or .csv formats) to a JavaScript variable as a string using only JavaScript? If so, could you prov

Answer 1

Here is a quick and dirty example based on a form named "myform" that contains a file input named "myfile" :

document.forms['myform'].elements['myfile'].onchange = function(evt) {
    if(!window.FileReader) return; // Browser is not compatible

    var reader = new FileReader();

    reader.onload = function(evt) {
        if(evt.target.readyState != 2) return;
        if(evt.target.error) {
            alert('Error while reading file');
            return;
        }

        filecontent = evt.target.result;

        document.forms['myform'].elements['text'].value = evt.target.result;
    };

    reader.readAsText(evt.target.files[0]);
};

Here's the associated HTML form:

  

    
    nothing loaded
  

and a jsfiddle to demo it.