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Make Denso QR Bar Code in Font PUTTING IT ALL TOGETHER

CHAPTER 12 PUTTING IT ALL TOGETHER
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addLoadEvent(prepareForms); To make the placeholder stand out, modify the color of the fields with the placeholder class in your color.css file: input.placeholder { color: grey; } Reload contact.html in a browser that doesn t support HTML5 to see the effects of the resetFields function. You ll find that your resetFields function produces the same effect as the HTML5 placeholder attribute does in an HTML5-enabled browser. Click any form field, or any label for that matter. The default value will disappear. If you move on to another field without entering anything, the default value reappears. If you insert something, the default value does not reappear.
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The next task that you re going to perform on the contact form involves one of the oldest uses of JavaScript. Client-side form validation has been around almost as long as JavaScript. The theory is simple. When a user submits a form, run some tests on the values provided. If required fields have not been filled in, the user is told with an alert box which fields need to be fixed. HTML5-enabled browsers have finally started to implement some native form validation for different types of fields. For example, in Opera 10, email input types are automatically validated:
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When you try to submit a form using an email input field, Opera automatically verifies it using RFCcompliant email validation, even if JavaScript isn't available. HTML5 also includes other types of validation, such as URLs entered into URL input fields. In these cases, you don t need to add any additional markup to the form; the browser will just validate it based on the input type. HTML5 also includes a required attribute that indicates that the value for the field is required and can t be left blank. Opera 10 also supports this feature without any additional scripting:
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CHAPTER 12 PUTTING IT ALL TOGETHER
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That s all good for browsers that support HTML5, but for your client s band site, you must be a little more flexible and include some JavaScript form validation as well. Adding JavaScript form validation sounds straightforward, and it usually is. But if JavaScript form validation is implemented badly, it can cause more harm than good. If the code has been written sloppily, the user may end up never being able to submit the form. There are three things to remember when you are writing JavaScript form-validation functions: Bad form validation can be worse than no validation at all. Never rely solely on JavaScript. It s not a substitute for server-side validation. Just because you validate a form with JavaScript doesn t mean you shouldn t check the values again when they are sent to the server. Client-side validation is about helping users properly fill out the form and not waste their time with an incomplete submission. Server-side validation is about protecting the database and underlying systems.
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It s best to keep form validation as simple as possible. To begin, you can just check whether the user has provided any value at all. The following function, isFilled, takes an element from a form as its single argument. function isFilled(field) { if (field.value.replace(' ','').length == 0) return false; var placeholder = field.placeholder || field.getAttribute('placeholder'); return (field.value != placeholder); } By checking the length of the value property after removing the spaces, you can see if the value has more than zero characters (and it's not all spaces). If it does not contain characters, the function returns a value of false. Otherwise, it continues on to the next comparison. By comparing the value property to the placeholder property, you can find out if the user has simply left the placeholder text in the field. If the two values are the same, the function returns a value of false. If both tests are passed, the field has been filled in, and the isFilled function returns a value of true. Next is a similar function called isEmail. It does a very crude test to check if the value of a form field looks like an email address. function isEmail(field) { return (field.value.indexOf("@") != -1 && field.value.indexOf(".") != -1); } This function runs two tests using the indexOf method. This method finds the first occurrence of a string within another string. If the search string is found, it returns the position. If the search string isn t found, it returns a value of -1. The first test looks for the @ character in the value property of the form field. This character must be present in an email address. If the @ isn t found, the isEmail function returns a value of false. The second test works exactly the same way, except this time the test is looking
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