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JavaScript The Solution

Meg Cusack
Meg Cusack
11,448 Points

Two questions. Why does "undefined" show up? How to indent a block of code?

My code is identical to his but after I get the "reload the page message", the code still runs and I get the word "undefined" printed on my screen. Also, I saw him highlight several lines of code and indent them all at once. How is he doing that? Here is my code:

// declare program variables
var num1;
var num2;
var message;

// announce the program
alert("Let's do some math!");

// collect numeric input
num1 = prompt("Please type a number");
num1 = parseFloat(num1);
num2 = prompt("Please type another number");
num2 = parseFloat(num2);
if ( num2 === 0) {
    alert("The second number is 0. You can't divide by zero. Reload and try again.");
} else if (isNaN(num1) || isNaN(num2)){
   alert("At least one of the values you typed is not a number. Reload the page and try again.");
else {

// build an HTML message
message = "<h1>Math with the numbers " + num1 + " and " + num2 + "</h1>";
message += num1 + " + " + num2 + " = " + (num1 + num2);
message += "<br>";
message += num1 + " * " + num2 + " = " + (num1 * num2);
message += "<br>";
message += num1 + " / " + num2 + " = " + (num1 / num2);
message += "<br>";
message += num1 + " - " + num2 + " = " + (num1 - num2);

// write message to web page

2 Answers

Steven Parker
Steven Parker
228,991 Points

You see "undefined" because the final line is outside of the "else" block, and still runs even when the calculations are not done.

In a workspace, when you have a block of code highlighted, you can hold "control" and type close bracket ("Ctrl-]") to indent the block. Control with open bracket ("Ctrl-[") will move code back to the left.