<!DOCTYPE html> <html> <head> <script> function myFunction() { document.getElementById("demo").innerHTML = "Paragraph changed."; } </script> </head> <body> <h2>JavaScript in Head</h2> <p id="demo">A Paragraph.</p> <button type="button" onclick="myFunction()">Try it</button> </body> </html>
<!DOCTYPE html> <html> <body> <h2>JavaScript in Body</h2> <p id="demo">A Paragraph.</p> <button type="button" onclick="myFunction()">Try it</button> <script> function myFunction() { document.getElementById("demo").innerHTML = "Paragraph changed."; } </script> </body> </html>
<!DOCTYPE html> <html> <body> <h2>External JavaScript</h2> <p id="demo">A Paragraph.</p> <button type="button" onclick="myFunction()">Try it</button> <p>(myFunction is stored in an external file called "myScript.js")</p> <script src="myScript.js"></script> <script src="https://www.w3schools.com/js/myScript.js"></script> <script src="/js/myScript.js"></script> </body> </html>
writing into the html output / html elemnt / window alert box/ browser console
JavaScript: Where to Insert JavaScript and output
原文：https://www.cnblogs.com/Nyan-Workflow-FC/p/10609295.html