Sum numbers from the visitor
importance: 5
Create a script that prompts the visitor to enter two numbers and then shows their sum.
P.S. There is a gotcha with types.
let a = +prompt("The first number?", "");
let b = +prompt("The second number?", "");
alert( a + b );
Note the unary plus + before prompt. It immediately converts the value to a number.
Otherwise, a and b would be string their sum would be their concatenation, that is: "1" + "2" = "12".