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Tip of the Day
Language: Web
Expertise: Intermediate
May 13, 1999

Easily Intercept, Validate, and Submit a Form With JavaScript

You can easily write JavaScript routines to validate form items before the form is submitted. Just define a form tag with a name and an action. The key is to add the onsubmit event to call your validating JavaScript code. Within the validating function, return false if the validation fails. In this example, when the user clicks the submit button, the onsubmit event calls the JavaScript function "validate". If the validation fails, the function returns false, and the submit is cancelled. You can also highlight the entire text field and give it focus, making the correction process easier for your user.
 
<html>
<head>
<script language=javascript>
function validate(obj){
  if ((obj.value<1) || (10<obj.value)){
    alert("Please try again");
    obj.select();
    obj.focus();
    return false;
  }
}
</script>
</head>
<body>
<form name="myform" onsubmit="return validate(this.txt1)" action="nextpage.asp">
  <p>Please Enter a number between 1 and 10:
  <input type=text name=txt1>
  <input type=submit>
</form>
</body>
</html>
William Wen
 
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