<script>
function readTextFile(file)
{
//alert("test");
    var rawFile = new XMLHttpRequest();
    rawFile.open("GET", file, false);
    rawFile.onreadystatechange = function ()
    {
        if(rawFile.readyState === 4)
        {
            if(rawFile.status === 200 || rawFile.status == 0)
            {
                var allText = rawFile.responseText;
                allTextArray = allText.split('\n');
                //alert(allText);
                var randomLine = Math.floor( Math.random() * allTextArray.length );
                //alert(allTextArray[randomLine]);
                document.getElementById("test").innerHTML=allTextArray[randomLine];
                return allTextArray[randomLine];
            }
        }
    }
    rawFile.send(null);
}
</script>
<script>
function test()
{
    alert(readTextFile('test.txt'));
    document.getElementById("test2").innerHTML= readTextFile('test.txt');
}
</script>


<button id="button_feedback" onclick="readTextFile('test.txt')"> test </button>
<button id="button_feedback2" onclick="test()"> test2 </button>
<div id="test">test</div>
<div id="test2">test2</div>