I can't use else in my script; how can I implement an if else statement without using else?

I'm trying to resize a div:

function hideTable(){

    var table = document.getElementById('PDemo');

    if(table.style.width == "50%") table.style.width = "150px";

    if(table.style.width == "150px") table.style.width = "50%";

}

This script doesn't work because as soon as the first if statement is executed, the condition for the second if statement becomes true, so that executes too, and thus nothing changes.