1    let explanation = document.getElementById("explanation");
2    let input = document.getElementById("input");
3    let button = document.getElementById("button");
4    let output = document.getElementById("output");
5    let select = document.getElementById("service");
6    
7    explanation.innerHTML = "Enter the cost of your meal. ";
8    explanation.innerHTML += "Then press Calculate. ";
9    button.onclick = calculateTip;
10   
11   function calculateTip()
12   {
13     let cost = parseFloat(input.value);
14     let percent = parseFloat(select.value);
15     let tip = cost * percent / 100;
16     tip = tip.toFixed(2);
17     let text = "A " + percent + "% tip is $" + tip;
18     output.innerHTML = text;
19     let total = cost + parseFloat(tip);
20     output.innerHTML += "<br>The total cost is $" + total;
21   }
22