JavaScript error with eventListener

I'm getting an error which I'm not quite sure what to make of. Anyway, before I go on to that, I found out about Unobtrusive JavaScript, at first I was just going to add an "OnClick" to my HTML but then found out that isn't a very good thing to do.

Anyway, so I did that and turned up with this code which isn't quite finished yet, but I wanted to try it out anyway before I went in and made any other changes.

    window.onload = function findSubmitButton(){
    var button = document.getElementsByClass("send_info").addEventListener("click", retrieveInputText());
}   

function retrieveInputText(){
    var inputArray = document.querySelectorAll("#container_id input[type=text]");
    var finalArray;
    for (var i in inputArray){
        if(inputArray[i].type == "text"){
            finalArray.push(i);
        }
    alert("done");
    }
}

The error chrome's console gives me is this: Uncaught TypeError: undefined is not a functionfindInputs.js:5 findSubmitButton

There was also something I wanted to know, I want to be able to use this script with any other sort of input form, so instead of directly identifying the button for this page, I used a class identifier, this way, it works with any page. The only way there would be any issues would be if I had two buttons of the sort, as it is right now, any page with that sort of information only has one button for such procedures. I would appreciate if someone helped me out with this, I'm new to JavaScript.