Why is FileReader.readAsText() returning null?

问题

I am trying to read a file in the same directory of an HTML and JavaScript file however it seems to be returning null. Below I have added the code I have from each file.

HTML File:

<html>
    <!-- Code to call the Google Maps API and link style.css sheet -->
<body>
    <div class="content">
        <div id="googleMap"></div>
        <div id="right_pane_results">hi</div>
        <div id="bottom_pane_options">
            <button onclick="get_parameters()">Try It</button>
        </div>
    </div>
</body>
<script type="text/javascript" src="./javascript.js">
    </script>
</html>

JavaScript File:

function get_parameters() {
    alert("hi"); // Just to let me know the function is getting called
    var freader = new FileReader();

    var text;
    freader.onload = function(e) {
        text = freader.result; 
    }
    freader.readAsText('./test.txt', "ISO-8859-1");
    text = freader.result; // To my knowledge, this should be taking the current line freader is on and storing it into text

    var div = document.getElementById('bottom_pane_options');
    div.innerHTML = div.innerHTML + text;
}

test.txt

Iron
Aluminum
Steel
//etc. for x number of times (depends on data I have parsed previously)

All I would like is for JavaScript to read test.txt and parse it into an array (text). The issue is, when I click the button 'Try It', the alert pops up (telling me the function is being called) and text contains null. I am running all files off my computer and all are in the exact same directory.

来源：https://stackoverflow.com/questions/21149113/why-is-filereader-readastext-returning-null

标签

javascript

file-io

null

filereader

local-files