Javascript：未捕获的类型错误：无法设置 null 的属性“innerHTML”
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Javascript: Uncaught TypeError: Cannot set property 'innerHTML' of null
提问by Tan WS
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
我浏览了几个问题，但找不到任何帮助。顺便说一下，这是我第一次在这里提问，所以我可能不会以正确的方式提问。无论如何，以下行导致了我的问题
/* cursorPps defined above */
document.getElementById("cursorPps").innerHTML = cursorPps;
The cursorPpsvariable is already defined. Can someone point out what other possible stuff could have caused this error?
的cursorPps变量已定义。有人可以指出其他可能导致此错误的原因吗？
Edit: By the way the problem is that it is not updating the value on HTML, although the value of the variable changes.
编辑：顺便说一下，问题是它没有更新 HTML 上的值，尽管变量的值发生了变化。
HTML:
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()"> Buy Cursor </div>
</div>
<script src="main.js"></script>
</body>
</html>
Javascript:
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);
回答by leopic
Make sure that
确保
- 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
- 您有一个元素具有该 ID
- 在运行 Javascript 之前页面上的元素是
- 您将 JS 的执行绑定到在元素位于页面上之后发生的事件（上一个的后续）
- 已填充 cursorPps 变量
Here's a simple codepen that demonstrates a way to do it http://codepen.io/leopic/pen/wDtIB
这是一个简单的 codepen，演示了一种方法http://codepen.io/leopic/pen/wDtIB
回答by GLES
<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)
您有一个具有该 ID 的元素
var length = document.querySelectorAll('#myDiv').length; if(length > 0) { // This element exists in the DOM tree }您将 JS 的执行绑定到在元素位于页面上之后发生的事件（上一个的后续）
<body> <div id="myDiv"></div> <script> var length = document.querySelectorAll('#myDiv').length; console.log(length); </script> </body>已填充 cursorPps 变量
if(cursorPps != undefined)
