How to ask a user to guess a number between 1 - 1000

Question

I'm trying to write some javascript code that asks the user to guess a number from 1 to 1000 and enter it into the prompt box. If the user guesses right, an alert box will pop up saying they got it right. If they guess wrong, another alert box will popup and say that they are wrong and to try once more.

The issue here is that I don't know what I have to do to make the code loop infinitely until they get the right answer. Here's what i have so far:

var a = 489; // the number that needs to be guessed to win the game.//var b stores whatever value the user enters.var b = prompt("Enter a number in between 1 and 1000");// if/else statement that test if the variables are equal.if (b == a) {alert("You're right!");} else {alert("Incorrect! Try again!");}

Best Answer

Just stick your prompt in some kind of loop. The code will inside the loop will run over and over until the comparison is false.

Basic example:

http://jsfiddle.net/s2he1twj/

var a = 500,b;while (parseInt(b) !== a) {b = prompt('Enter a number!');if (b === null) break;}

while loop

Do this recursively by calling the same function like

var a = 489;function promptGuess(){//var b stores whatever value the user enters.var b = prompt("Enter a number in between 1 and 1000");// if/else statement that test if the variables are equal.if (b == a){alert("You're right!");} else {alert("Incorrect! Try again!");promptGuess();}}promptGuess();

Use a while until the match:

var a = 489; var b;while(b != a) {var b = prompt("Enter a number in between 1 and 1000");if (b == a) {alert("You're right!");} else {alert("Incorrect! Try again!");}}

One more thing: although the b != a evaluation is correct, it's error-prone. The != operator do conversion type, whilst the !== operator compares types and value.

In your case: 5 != '5' will return false, but 5 !== '5' returns true. It's recommended that your comparisons be conversion-free. It's more strict.

In your case, this means:

while(parseInt(b) !== a)

Greetings!

Accepted Answer

Number matching

Basically, when you make prompt, it returns a String or text, not a number. To fix this, do:

if (parseInt(b,10) === a) {//Code}

Other ways

They're a lot of ways to parse numbers. Here's a few more:

parseFloat(b); // Also parses decimals: '5.3' -> 5.3

parseInt(b, 10); // Gives an integer (base 10): '5.3' -> 5

+b; // A very 'short' way; '5.4' -> 5.4

Number('5.4e2'); // Number case: '5.4e2' -> 540

Looping

Now to repeat? Make it a loop!

var a = 432;while (true) {var b = prompt("Enter a number in between 1 and 1000");if (b == a){alert("You're right!");break; // Stops loop} else if (!b) { break; } else {alert("Incorrect! Try again!");}}

Not sure why, but some people hate while true loops. They shouldn't cause any problems as long as you coded it properly

Random Numbers

You can get a random number using Math.random.

var min = 1,max = 1000;Math.floor(Math.random() * (max - min + 1)) + min;

If you're like me and want short code, you can shorten it by:

Math.floor(Math.random() * (999)) + 1;

All Together Now!

var a = Math.floor(Math.random() * (999)) + 1;while (true) {var b = prompt("Enter a number in between 1 and 1000");if (b == a) {alert("You're right!");break; // Stops loop} else if (!b) {alert("The Correct Answer was: " + a); //Shows correct answerbreak;} else {alert("Incorrect! Try again!");}}