JavaScript: Write HTML output
Example
document.write("<h1>This is a heading</h1>");
document.write("<p>This is a paragraph</p>");Tip: You can only use document.write with HTML output. If you use this method after the document is loaded, the entire document will be overwritten.
JavaScript: react to events
Example
<button type="button" onclick="alert('Welcome!')">点击这里</button>alert() function is not commonly used in JavaScript, but it is very convenient for code testing.
The onclick event is just one of many events you'll learn about in this tutorial.
JavaScript: Change HTML content
Using JavaScript to process HTML content is extremely powerful.
Example
x=document.getElementById("demo") //查找元素
x.innerHTML="Hello JavaScript"; //改变内容You will often see document.getElementByID("some id"). This method is defined in the HTML DOM.
DOM (Document Object Model) is the official W3C standard for accessing HTML elements.
JavaScript: Change HTML style
Changing the style of HTML elements is a variant of changing HTML attributes.
Example
x=document.getElementById("demo") //找到元素
x.style.color="#ff0000"; //改变样式JavaScript: Validate input
JavaScript is often used to validate user input.
Example
if isNaN(x) {alert("Not Numeric")};Scripts in HTML must be placed between the <script> and </script> tags.
Scripts can be placed in the
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