Variable not depleting javascript

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Hello! I am creating a game where you can buy pokemon. When the pokemon is bought, I obviously want the coins variable to drop by the # of coins the pokemon costs. However, when I do this, the coins variable always stays at 1000 and does not drop when I buy the pokemon. Here is the function that is used when onclick on a button:

function buymagikarp() {
  if(coins >= 100 ) {
    swal("Success", "You bought 1 magikarp!", "success");
    coins - 100;
    pokemonchosen.push("Magikarp");
  } else {
    swal("Error", "Not enough balance", "error");
  }
}

What I have tried:

I have tried to remove the swal("") to see if the alerts were messing up the coins variable.

Posted 1-Aug-17 4:41am

Member 13257242

Updated 1-Aug-17 4:51am

OriginalGriff

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Member 13257242 1-Aug-17 10:52am

After tweaking the code a bit, I took a step backward and a step forward. I added in local storage:

function getName() {
var coins;
if(localStorage.getItem('coins') === null) {
localStorage.setItem('coins', coins);
} else {
coins = localStorage.getItem('coins');
}
document.getElementById("p1").innerHTML = "Coins: " + coins;
}

Now, the coins actually deplete, and they save after page reload but they still always show up as 1000 even in the console when I type in coins it shows that they depleted? This is honestly really confusing to me.

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Thomas Daniels · Answer 1 · 2017-08-01T04:51:00

Solution 1

coins - 100 just calculates the value, but never stores it. Did you mean:

JavaScript

coins -= 100; // (equivalent of:) coins = coins - 100;

?

Posted 1-Aug-17 4:51am

Thomas Daniels

Updated 1-Aug-17 4:52am

v2

Comments

Member 13257242 1-Aug-17 10:54am

After tweaking the code a bit, I took a step backward and a step forward. I added in local storage:

function getName() {
var coins;
if(localStorage.getItem('coins') === null) {
localStorage.setItem('coins', coins);
} else {
coins = localStorage.getItem('coins');
}
document.getElementById("p1").innerHTML = "Coins: " + coins;
}

Now, the coins actually deplete, and they save after page reload but they still always show up as 1000 even in the console when I type in coins it shows that they depleted? This is honestly really confusing to me.

Thomas Daniels 1-Aug-17 10:55am

Where are you defining coins? Are you also defining it outside of getName? In that case, the 'coins' in getName probably shadows the 'coins' outside of getName.

Member 13257242 1-Aug-17 11:07am

I am defining coins outside at the top of the code.

var coins = 1000;

Thomas Daniels 1-Aug-17 11:09am

Well, then you don't need the 'var coins;' line in getName().

Member 13257242 1-Aug-17 11:12am

Even after removing var coins; , it still won't deplete

Thomas Daniels 1-Aug-17 11:22am

Are you calling the localStorage setter every time you change the coins variable? Do you change the HTML element every time you do so?

Member 13257242 1-Aug-17 11:56am

How would I change the localStorage setter? With a while loop? I am using this code to start the localstorage:

Member 13257242 1-Aug-17 11:56am

is the code I am using to start up the LocalStorage.

Member 13257242 1-Aug-17 12:00pm

body onload="getName();"

Member 13257242 1-Aug-17 12:01pm

with tags of course, for some weird reason codeproject isn't displaying the tags.

Thomas Daniels 1-Aug-17 12:02pm

Every time you change the value of 'coins', you need to:

Call 'setItem' for localStorate
Change the HTML content of the element displaying the value

If you do not do that, the 'coins' value will not be kept after refresh.

Member 13257242 1-Aug-17 13:25pm

Which HTML content? To display the coins variable, I am using a paragraph with an id of p1 to display. How would I change that? it is document.getElementById('p1').innerHTML = "Coins: " + coins;

Thomas Daniels 1-Aug-17 14:14pm

Yes, it's that, but you need to do that _every time you update the 'coins' variable, otherwise the changes won't be reflected_.

Member 13257242 1-Aug-17 10:54am

Thanks for the answer ProgramFox, it really helped!