JavaScript基础－3
在javascript中有一个非常重要的对象就是DOM对象，DOM对象起到了对页面中的对象进行操作，我们许多效果与功能都要通过DOM实现。
有以下常用的基本对象：
数字对象：Number
字符串对象：String
数组对象：Array
数学对象：Math
日期对象：Date
全局对象：Global
- Number对象的demo:
1: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
2: <html>
3: <head>
4: <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
5: <title>Untitled Document</title>
6: <script type="text/javascript">
7: alert("Number的最大数是："+Number.MAX_VALUE);
8: alert("Number的最小数是："+Number.MIN_VALUE);
9:
10: </script>
11: </head>
12: <body>
13: </body>
14: </html>
- String对象的demo:
1: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
2: <html>
3: <head>
4: <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
5: <title>Untitled Document</title>
6: <script type="text/javascript">
7: function TestString(){
8: alert("我们开始试验String对象");
9:
10: var txtStringValue = document.getElementById("txtStringDemo").value;
11: alert("TextBox中的值是" + txtStringValue);
12:
13: alert("TextBox中的第一字符的值是" + txtStringValue.charAt(0));
14: for(i=0;i<txtStringValue.length;i++)
15: {
16: alert("第"+i+"字符的值是"+txtStringValue.charAt(i));
17: }
18: alert("将TextBox中第一字符转化为ASCII码" + txtStringValue.charCodeAt("0"));
19:
20:
21:
22: }
23: </script>
24: </head>
25: <body>
26: <form id="StringFormDemo">
27: <input type="text" id="txtStringDemo" value="">
28: <input type="button" id="btnSubmint" value="试验字符串对象" onclick="TestString()">
29: </form>
30: </body>
31: </html>
1: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
2: <html>
3: <head>
4: <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
5: <title>Untitled Document</title>
6: <script type="text/javascript">
7: function TestString(){
8:
9: var txtStringValue = document.getElementById("txtStringDemo").value;
10:
11: alert("txtStringDemo中的值是" + txtStringValue);
12:
13: var filenameExt = txtStringValue.substring(txtStringValue.lastIndexOf(".") + 1);
14:
15: alert("FileName extense:" + filenameExt);
16: //比较之前先转化成为小写的字母
17: if (filenameExt.toLowerCase() != "jpg") {
18: alert("对不起只支持jpg上传");
19: }
20: else {
21: alert("上传成功！");
22: }
23:
24:
25: }
26:
27: function ChangeName(){
28: var txtStringValue = document.getElementById("txtStringDemo").value;
29:
30: var filename = txtStringValue.substring(txtStringValue.lastIndexOf("\\") + 1);
31: var txtFile=document.getElementById("txtFileName");
32: txtFile.value=filename;
33: }
34: </script>
35: </head>
36: <body>
37: <form id="StringFormDemo">
38: <input type="file" id="txtStringDemo" value="" onchange="ChangeName()">
39: <input type="text" id="txtFileName">
40: <input type="button" id="btnSubmint" value="试验字符串对象" onclick="TestString()">
41: </form>
42: </body>
43: </html>
