Validating numeric input
Depending on browser support, the url field can be automatically validated when submitted.Some smartphones recognize the url type, and adds ".com" to the keyboard to match url input.Most current web browsers support this attribute and will communicate missing required input to the user, using standard web browser dialog mechanisms.These dialogs are expected to respect the settings and preferences of the user in the web browser (and operating system), such as default font-size, colors, and language.HTML5 defines a range of built-in functionality to validate common types of input, such as email addresses and dates.In some situations, such as validating custom controls or supporting legacy browsers, additional scripting may be necessary to validate user input.
A regular expression is sometimes called regex or regexp. \.[a-z A-Z]$ “ matches an email address, so you can use this pattern to validate if a specific string is equals to a valid email address or not. Regual Expressions namespace So let’s start, Now you can fill the fields then click check button, if there is any invalid data a message box will appear and tell you. So as a software developer you should know that there are two types of users, Also imagine that you have a web application and there is a form to add a new article, this form contains a text box to enter the title of the article which will render as a label when the users will read the article, if one of the users write “Some text” in the field, this will cause a big problem because when the users will open the article instead of seeing the title they will see a link that is maybe a dangerous link.So checking what users write in your app fields is very important aspect to build a robust and secure apps.As a developer you create a form like this and put a label beside each field to tell the user that you should enter your zip code in this field, but actually not all the users follow the labels and enter what you are waiting for, sometimes one of the users will enter a fake email address or even enter some letters that don’t refer to anything like “abcdef” as Phone number, this mistake will lead to some problems.After adding this value to the database and dealing with it in another place, for example if you want to send this user an sms message, in this situation your system will try to send a message to this phone number “abcde”, it’s not only a fake phone number it’s something not related even to numbers.
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Instead, it will display a message that is generated by the web browser itself.