I have recently been struggling with a calculator concept using JavaScript. I've tried lots of things, but just can't get it to work. 

The calculator has three drop down lists: one for the first number (0-9), one for the operation and one for the second number (also 0-9). Basically, when you press the "Perform Equation" button, it gets the values of the drop down lists and supposedly adds up all those values, performing an equation. Here's an example, short and simple.

```
<select id="n1">
<option value="0">0</option>
<option value="1">1</option>
</select>

<select id="op">
<option value="+">0</option>
<option value="-">1</option>
</select>

<select id="n2">
<option value="0">0</option>
<option value="1">1</option>
</select>
<input type="button" value="Perform Equation" onclick="perform"/>

<p id="printE"/>

<script>
function perform() {
var analyseN1 = document.getElementById("n1").value
var analyseOp = document.getElementById("op").value
var analyseN2 = document.getElementById("n2").value
var addUp = analyseN1+analyseOp+analyseN2;
document.getElementById("printE").innerHTML= addUp;
}
</script>

```

As you can see, I get the values of all the drop downs, "add them up" and then print the final result. It's not working, however. Can someone please tell me why? I'm, well, not the best at JavaScript. I'm rather young and got introduced to the language only a couple of months ago. So yeah, if you know the answer, it would be awesome if you could tell me. Thanks!