Javascript基本语法与C/Java非常相似,比较特殊的是,Javascript有一个for-in语句,可以用来遍历对象中的属性。
<script> var person = {"name":"Bill Gates","age":56,"Country":"America"}; var text = ""; for (x in person){ text+=(person[x]+","); //使用person[x]取出person对象的x属性值 } document.write(text) </script>
代码整理自w3school:http://www.w3school.com.cn
效果图:
代码:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta http-equiv="Content-Language" content="zh-cn" /> <title>Javascript 基本语句(if-else/switch/for/while/for-in/try-catch)</title> <head> <style> body {background-color:#e5e5e5} </style> </head> <body> <h3>(一)if-else语句</h3> <p>点击按钮,显示当前是上午还是下午。</p> <button onclick = "timeNow()">确定</button> <p id = "timeText"></p> <script> function timeNow(){ var x; var time = new Date().getHours(); if (time<12){ x = "上午"; }else{ x = "下午"; } document.getElementById("timeText").innerHTML = x; } </script> <h3>(二)switch语句</h3> <p>点击按钮,显示当前是星期几</p> <button onclick = "weekdayNow()">确定</button> <p id = "weekdayText"></p> <script> function weekdayNow(){ var x; var time = new Date().getDay(); switch (time){ case 0: x = "Sunday"; break; case 1: x = "Monday"; break; case 2: x = "Thesday"; break; case 3: x = "Wendsday"; break; case 4: x = "Thursday"; break; case 5: x = "Friday"; break; case 6: x = "Saturday"; break; default: x = "Unknown"; break; } document.getElementById("weekdayText").innerHTML = x; } </script> <h3>(三)for语句</h3> <script> var cars = ["BMW","Volvo","Saab"] for (var i =0;i<cars.length;i++){ document.write(cars[i]+"<br/>"); } </script> <h3>(四)for/in语句:遍历对象的属性</h3> <script> var person = {"name":"Bill Gates","age":56,"Country":"America"}; var text = ""; for (x in person){ text+=(person[x]+","); //使用person[x]取出person对象的x属性值 } document.write(text) </script> <h3>(五)while语句</h3> <script> var i = 0; while(i<5){ document.write("hello world-"+i+"<br/>"); i++; } </script> <p>非boolean值作为while的条件:</p> <script> var cars = ["BMW","Volvo","Saab"] var i = 0; while(cars[i]){ document.write("cars["+i+"]="+cars[i]+","); i++; } </script> <p>注:break,continue语句与C/java完全相同</p> <h3>(六)try-catch语句</h3> <button onclick = "errTest()">点击按钮</button> <script> function errTest(){ try{ alertttt("hello"); }catch(err){ var text = "网页上有一个错误。\n错误描述:"; text+=err.message; alert(text) } } </script> </body> </html>
时间: 2024-09-30 20:38:05