Welcome to the Bod's World 2 JavaScript Form Tester.

1   <script language="javascript">
2   <!--
3   function formchecker(theForm) {
4	var allvalid = true;
5	var alertstr = "";
6	var validstr = "All form data is correct.\n\n";
7	var num_of_elements = theForm.length;
8	var radio_selected = false;
9	var checkbox_selected = false;
10
11	for (var i=0; i<num_of_elements; i++) {
12		var theElement = theForm.elements[i];
13		var element_type = theElement.type;
14		var element_name = theElement.name;
15		var element_value = theElement.value;
16
17  // Check Text boxes ...
18		if (element_type == "text") {
19			var checkstr = 
			  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+-
			  /*,.'@~#%$£€!µ°±(){}[ ]";
20			if (element_value.length == 0) {
21				alertstr += "Form element '" 
				  + element_name + "' contains no data.\n\n";
22				allvalid = false;
23			} else {
24				var badchars = "";
25				for (var j=0; j<element_value.length; j++) {
26					for (var k=0; k<checkstr.length; k++) {
27						if (element_value.charAt(j) == 
						  checkstr.charAt(k)) {
28							break;
29						}
30					}
31					if (k == checkstr.length) {
32						for (var l=0; l<badchars.length; l++) {
33							if (element_value.charAt(j) == 
							  badchars.charAt(l)) {
34								break;
35							}
36						}
37
38						if (l == badchars.length) {
39							badchars += element_value.charAt(j);
40						}
41						allvalid = false;
42					}
43				}
44				if (!allvalid) {
45					alertstr += "Form element '" + element_name + 
					  "' contains the following illegal characters ...\n\t" 
					  + badchars + "\n\n";
46				}
47			}
48			if (allvalid) {
49				validstr += "Into form element '" + element_name + 
				  "' you entered the text ...\n\"" + element_value + "\".\n\n";
50			}
51		}
52
53  // Check Textarea boxes ...
54		if (element_type == "textarea") {
55			var checkstr = 
			  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+-
			  /*,.'@~#%$£€!µ°±(){}[ ]\n\r\f";
56			if (element_value.length == 0) {
57				alertstr += "Form element '" + element_name + 
				  "' contains no data.\n\n";
58				allvalid = false;
59			} else {
60				var badchars = "";
61				for (var j=0; j<element_value.length; j++) {
62					for (var k=0; k<checkstr.length; k++) {
63						if (element_value.charAt(j) == 
						  checkstr.charAt(k)) {
64							break;
65						}
66					}
67					if (k == checkstr.length) {
68						for (var l=0; l<badchars.length; l++) {
69							if (element_value.charAt(j) == 
							  badchars.charAt(l)) {
70								break;
71							}
72						}
73
74						if (l == badchars.length) {
75							badchars += element_value.charAt(j);
76						}
77						allvalid = false;
78					}
79				}
80				if (!allvalid) {
81					alertstr += "Form element '" + element_name + 
					  "' contains the following illegal characters ...\n\t" 
					  + badchars + "\n\n";
82				}
83			}
84			if (allvalid) {
85				validstr += "Into form element '" + element_name + 
				  "' you entered the text ...\n\"" + element_value + "\".\n\n";
86			}
87		}
88
89  // Check Drop-down lists ...
90		if (element_type.indexOf("select") > -1) {
91			var index = theElement.selectedIndex;
92			if (index <= 0) {
93				alertstr += "The first option in form element '" + element_name + 
				  "' is not valid.\n\n";
94				allvalid = false;
95			}
96			if (allvalid) {
97				validstr += "From form element '" + element_name + 
				  "' you selected option \"" + theElement.options[index].value + 
				  "\".\n\n";
98			}
99		}
100
101  // Check Radio buttons ...
102		if (element_type == "radio" ) {
103			if (theElement.checked == true) {
104				radio_selected = true;
105				validstr += "From form element '" + element_name + 
				  "' you selected the \"" + element_value + "\" button.\n\n";
106			}
107		}
108
109 // Check Checkboxes ...
110		if (element_type == "checkbox") {
111			if (theElement.checked == true) {
112				checkbox_selected = true;
113				validstr += "From form element '" + element_name + 
				  "' you selected the \"" + element_value + "\" checkbox.\n\n";
114			}
115		}
116
117 // Check Buttons ...
118		if (element_type == "button") {
119			// Don't check buttons - use the onClick event to invoke functions.
120		}
121
122 	// .... End of loop through form elements ....
123	}
124
125	if (radio_selected == false) {
126		alertstr += "There is no Radio Button selected.\n\n";
127		allvalid = false;
128	}
129
130	if (checkbox_selected == false) {
131		alertstr += "There are no Checkboxes selected.\n\n";
132		allvalid = false;
133	}
134
135 // All elements checked - now determine if form is OK ...
136	if (allvalid) {
137		alert (validstr);
138		alert ("Who's a clever-clogs then?\n\n        %%%\n     / o     o \\\n    @   \\
		  /   @\n      \\  ~~  /\n         ###");
139		return false;
140	} else {
141		alert (alertstr);
142		return false;
143	}
144 }
145 //-->
146 </script>

The basic way this script works is to loop through all the form elements and check for the type of each element - the method of checking depends on this.