HTML select drop box with if statement and alert box

I want to make an HTML select drop box with 25 options.
After selection I want with a command button to show an alert box showing the type of the selection.
Options are divided to three (3) types:

• Options 1-10 = TYPE1
• Options 11-20 = TYPE2
• OPTIONS 21-25 = TYPE3

Below is my html code that does not work…

<select id="item1" name="Item 1">
<OPTION VALUE="0"> Select...</OPTION>
<OPTION VALUE="1">option1</OPTION>
<OPTION VALUE="2"> option2</OPTION>
<OPTION VALUE="3"> option3</OPTION>
<OPTION VALUE="4"> option4 </OPTION>
<OPTION VALUE="5">option5</OPTION>
<OPTION VALUE="6">option6</OPTION>
<OPTION VALUE="7">option7</OPTION>
<OPTION VALUE="8">option8</OPTION>
<OPTION VALUE="9">option9</OPTION>
<OPTION VALUE="10">option10</OPTION>
<OPTION VALUE="11">option11</OPTION>
<OPTION VALUE="12">option12</OPTION>
<OPTION VALUE="13">option13</OPTION>
<OPTION VALUE="14">option14</OPTION>
<OPTION VALUE="15">option15</OPTION>
<OPTION VALUE="16">option16</OPTION>
<OPTION VALUE="17">option17</OPTION>
<OPTION VALUE="18">option18</OPTION>
<OPTION VALUE="19">option19</OPTION>
<OPTION VALUE="20">option20</OPTION>
<OPTION VALUE="21">option21</OPTION>
<OPTION VALUE="22">option22</OPTION>
<OPTION VALUE="23">option23</OPTION>
<OPTION VALUE="24">option24</OPTION>
<OPTION VALUE="25">option25</OPTION>
<OPTION VALUE="25">option26</OPTION>
</select>

<button onclick="message()">Find your Type</button>

<SCRIPT>

function message() {

var s = document.getElementById('item1');
var item1 = s.options[s.selectedIndex].value;

if (item1 = 1) {
    alert("Type1")
}
else if (item1 = 10) {
    alert("Type1")
}
else if (item1 = 11) {
    alert("Type2")
}
}
else if (item1 = 20) {
    alert("Type2")
}
else if (item1 = 21) {
    alert("Type3")
}
}
else if (item1 = 25) {
    alert("Type3")
}
}
</SCRIPT>

Also is there a shorter way to do it right?
Thanks!