JavaScript：需要帮助订购我的JS“未捕获的TypeError：无法读取null的属性'值' [英] JavaScript: Need help ordering my JS "Uncaught TypeError: Cannot read property 'value' of null"
问题描述
我得到Uncaught TypeError：
无法读取null的属性'value'。
问题在于我的js命令和它调用DOM的顺序，但我不确定究竟在哪里。
有人在帮助我指出正确的方向
以下是我的代码：
< title>< ; /标题>
< / head>
< body>
< form>
< input id =todoItemtype =textplaceholder =Todo Item/>
< input type =buttonvalue =Saveonclick =insert（）; />
< / form>
< div id =display>< / div>
< script type =text / javascriptsrc =main-2.js>< / script>
< / body>
< / html>
main-2.js：
var todos = [];
var todoInput = document.getElementById（todoItem）;
var messageBox = document.getElementById（display）;
函数insert（）{
todos.push（todoInput.value）;
clearAndShow（）;
}
函数clearAndShow（）{
todoInput.value =;
messageBox.innerHTML =;
messageBox.innerHTML + =标题：+ todos.join（，）+< br />;
}
把此行：
var todoInput = document.getElementById（todoItem）;
放入函数 insert
当var todoInput是init时，元素不存在。
function insert（） {
var todoInput = document.getElementById（todoItem）;
todos.push（todoInput.value）;
clearAndShow（）;
}
清除输入写这段代码
document.getElementById（todoItem）。value ='';
I am an amateur JS person so be kind with your voting as I am new to this.
I am getting Uncaught TypeError:
Cannot read property 'value' of null.
I realize the issue is with the order of my js and the order in which it is calling DOM, but I am not sure exactly where.
Someone mind helping point me in the right direction?
Here is my code:
<title></title>
</head>
<body>
<form>
<input id="todoItem" type="text" placeholder="Todo Item" />
<input type="button" value="Save" onclick="insert();" />
</form>
<div id="display"></div>
<script type="text/javascript" src="main-2.js"></script>
</body>
</html>
main-2.js:
var todos = [];
var todoInput = document.getElementById("todoItem");
var messageBox = document.getElementById("display");
function insert() {
todos.push(todoInput.value);
clearAndShow();
}
function clearAndShow() {
todoInput.value = "";
messageBox.innerHTML = "";
messageBox.innerHTML += "Titles: " + todos.join(", ") + "<br/>";
}
put this line:
var todoInput = document.getElementById("todoItem");
into the function insert
when the var todoInput is init the element not exists.
function insert() {
var todoInput = document.getElementById("todoItem");
todos.push(todoInput.value);
clearAndShow();
}
to clear input write this code
document.getElementById("todoItem").value='';
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