Friends who have just started to contact js must be exposed to the output of js, so they will definitely use document.write, alert, innerHTML, console.log. Here is a brief introduction. Friends in need can refer to it
JavaScript Output
JavaScript does not have any printing or output functions.
JavaScript displays data
JavaScript can output data in different ways:
Use window.alert() Pop up an alert box.
Use the document.write() method to write the content into the HTML document.
Use innerHTML Write to HTML element.
Use console.log() Write to the browser's console.
Use window.alert()
You can pop up an alert box to display data:
<!DOCTYPE html> <html> <body> <h1 id="我的第一个页面">我的第一个页面</h1> <p>我的第一个段落。</p> <script> window.alert(5 + 6); </script> </body> </html>
Manipulate HTML elements
such as To access an HTML element from JavaScript, you can use the document.getElementById(id) method.
Please use the "id" attribute to identify HTML elements, and innerHTML to get or insert element content:
<!DOCTYPE html>
<html>
<body>
<h1 id="我的第一个-nbsp-Web-nbsp-页面">我的第一个 Web 页面</h1>
<p id="demo">我的第一个段落</p>
<script>
document.getElementById("demo").innerHTML = "段落已修改。";
</script>
</body>
</html>The above JavaScript statement (in the <script> tag) can be executed in a web browser: <br/>document.getElementById("demo") is JavaScript code that uses the id attribute to find an HTML element. <br/>innerHTML = "Paragraph has been modified." is the JavaScript code used to modify the HTML content (innerHTML) of the element. <br/><strong>In this tutorial<br/>In most cases, in this tutorial, we will use the method described above to output: <br/>The following example directly puts id="demo" The <p> element is written to the HTML document output: <br/><strong>Writing to HTML document<br/>For testing purposes, you can write JavaScript directly in the HTML document: </script>
<!DOCTYPE html> <html> <body> <h1 id="我的第一个-nbsp-Web-nbsp-页面">我的第一个 Web 页面</h1> <p>我的第一个段落。</p> <script> document.write(Date()); </script> </body> </html>
Please use document.write() to only write content to the document output.
If document.write is executed after the document has finished loading, the entire HTML page will be overwritten.
<!DOCTYPE html>
<html>
<body>
<h1 id="我的第一个-nbsp-Web-nbsp-页面">我的第一个 Web 页面</h1>
<p>我的第一个段落。</p>
<button onclick="myFunction()">点我</button>
<script>
function myFunction() {
document.write(Date());
}
</script>
</body>
</html>Write to console console.log()
If your browser supports debugging, you can use the console.log() method to display JavaScript values in the browser.
Use F12 in the browser to enable debugging mode, and click the "Console" menu in the debugging window.
<!DOCTYPE html> <html> <body> <h1 id="我的第一个-nbsp-Web-nbsp-页面">我的第一个 Web 页面</h1> <script> a = 5; b = 6; c = a + b; console.log(c); </script> </body> </html>
Example console screenshot:
The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
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