CODEWITHSUNDEEP
javascripthtml
Tan WS
Tan WS

Reputation: 181

Javascript: Uncaught TypeError: Cannot set property 'innerHTML' of null

I've browsed through a couple of questions but I couldn't find any help. By the way this is the first time I'm asking a question here so I might not do it the right way. Anyway, the following line is causing me the problem

/* cursorPps defined above */
document.getElementById("cursorPps").innerHTML = cursorPps;

The cursorPps variable is already defined. Can someone point out what other possible stuff could have caused this error?

Edit: By the way the problem is that it is not updating the value on HTML, although the value of the variable changes.

HTML:

<html>

<head>
<title>Potato Clicker</title>
<link rel="stylesheet" type="text/css" href="interface.css">
</head>

<body>

<div id="left">
<img id="potato-img" onClick="potatoClick(clickPower)" src="stockvault-potatoes107220.jpg" width="300" height="300">
<br>
<div id="mainDisplay">
<span id="potatoes">0</span> <br> potatoes
<br>
<br>
Producing <span id="pps">0</span> potatoes per second
<br>
</div>
Cursors: <span id="cursors">0</span>
</div>

<div id="middle">
<div id="buildings" onClick="buyCursor()"> &nbsp; Buy Cursor &nbsp; </div>
</div>


<script src="main.js"></script>
</body>

</html>

Javascript:

//variables

var potatoes = 0;   //potatoes
var clickPower = 1; //potatoes gained per click
var pps = 0;        //potatoes per second
var cursors = 0;    //cursors
var cursorCost;     //cost of cursor
var cursorPps = 0;  //total cursor potatoes per second
var cursorBuy;      //cursor buy button


//functions

function potatoClick(number) {

potatoes = potatoes + number;
document.getElementById("potatoes").innerHTML = potatoes;

}

function buyCursor() {

var cursorCost = Math.floor(10 * Math.pow(1.2,cursors));
if (potatoes >= cursorCost) {
pps = pps - cursorPps;
cursors = cursors + 1;
potatoes = potatoes - cursorCost;
cursorPps = cursorPps + 1;
pps = pps + cursorPps;
document.getElementById("potatoes").innerHTML = potatoes;
document.getElementById("cursors").innerHTML = cursors;
document.getElementById("cursorPps").innerHTML = cursorPps;
document.getElementById("pps").innerHTML = pps;
}
else {
alert("Not enough potatoes!")
}
var nextCost = Math.floor(100 * Math.pow(1.2,cursors));       
document.getElementById('cursorCost').innerHTML = nextCost; 
}

window.setInterval(function () {

if (pps > 0) {

potatoClick(pps);

}

}, 1000);

Upvotes: 2

Views: 12366

Answers (2)

Patt Mehta
Patt Mehta

Reputation: 4194

<div id="myDiv"></div>

  • You have an element with that ID

    var length = document.querySelectorAll('#myDiv').length;
if(length > 0) {
    // This element exists in the DOM tree
}

  • You bind the execution of your JS to an event (follow-up from previous) that happens after the element is on the page

    <body>
    <div id="myDiv"></div>
    <script>
        var length = document.querySelectorAll('#myDiv').length;
        console.log(length);
    </script>
</body>

  • The cursorPps variable has been populated

    if(cursorPps != undefined)

Upvotes: 2

leopic
leopic

Reputation: 3002

Make sure that

  • You have an element has that ID
  • The element IS on the page before that Javascript is run
  • You bind the execution of your JS to an event (follow-up from previous) that happens after the element is on the page
  • The cursorPps variable has been populated

Here's a simple codepen that demonstrates a way to do it http://codepen.io/leopic/pen/wDtIB

Upvotes: 3

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