1 . 外部JS文件引入 通过script标签中的src属性引入，在head标签中写 （重点）
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>js引入方式</title> <!-- 引入js --> <script src="js文件地址"></script> </head> <body> </body> </html>2. 写在页面内部 body 标签中
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>js引入方式</title> </head> <body> <script> </script> </body> </html>3. 写在事件的属性值中 这种不常用
1 . alert（）； 向网页弹出对话框 （弹窗方式）
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>js输出方式</title> </head> <body> <script> alert("终于等到你，还好没放弃"); </script> </body> </html>2 . document . write（"＂）； 向文档页面写入内容
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>js输出方式</title> </head> <body> <script> document.write("终于等到你，还好没放弃"); </script> </body> </html>
3. console.log(" ") ;向控制台输出 f12
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>js输出方式</title> </head> <body> <script> console.log(1152455515); // 如果是字符串的话 记得加双引号 " " </script> </body> </html>