In all cases, the form is called That's checking the value's equality with a null String (two single quotes with nothing between them).
When you are asking a reader for their email address, you can use a simple » address validation function to make sure the address has a valid structure. Each option in a drop-down box is indexed in the array Annoyingly, there is no simple way to check which radio button out of a group is selected — you have to check through each element, linked with Boolean AND operators .
Usually you'll just want to check if Keep Learning // Advanced DOMs → Go!
The option of using pure HTML, sometimes with a touch of CSS, to complement Java Script form validation was until recently unthinkable.
Obviously neither example is very limiting, but it will prevent people from entering completely wrong values, such as phone number, strings with multiple '@'s or spaces.
Here is how it appears in Safari (with our CSS formatting to show the (in)valid state): In a similar fashion to the Again, the input box appears as normal: This time the minimum requirement for most browsers is one or more letters followed by a colon. :[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f] | \[\x01-\x09\x0b\x0c\x0e-\x7f]) ) \])\z Or you can look here for more solutions.
It makes your page much more user-friendly, and takes out the frustration of having to fill out the same form repeatedly.
It's also very precise, as you can point out the exact field where there's a problem.
In other web browsers they can be used in combination with the .
You can do more validation on Server-Side as per your need to make your code more secure.
Use only My SQLi or PDO where possible because they are more secure than My SQL.
Different browsers may mark the input box in some way (Firefox 4 Beta adds a red box-shadow by default), display a warning (Opera) or even prevent the form from being submitted if this field has no value.
Hopefully these behaviours will converge in future releases.For these examples we have created our own valid/invalid CSS formatting to override the browser default. That's why you may see something like the following: Before you type anything into the box a red marker is shown.