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Validate an input value with the pattern attribute

Written byPhuoc Nguyen
06 Apr, 2021
Validating user input against specific rules is a common thing when we work with input fields. Without using an external validation library, we can use some built-in HTML 5 inputs to strict the value.
Specifically, the following input types force user to enter valid characters:
Input typeDescription
`type="color"`Only accepts a color
`type="date"`Only accepts a date
`type="email"`Only accepts a valid email address
`type="number"`Only accepts a number
`type="tel"`Only accepts a phone number
`type="url"`Only accepts a URL
Although these input types are useful, they can't serve the cases that the input must match a given regular expression.
For example, how we can force user to enter exactly 10 digits of a phone number when using the `type="tel"` attribute. That's where the `pattern` attribute comes in.
The sample code below solves the issue mentioned earlier:
<input type="tel" pattern="^\d{10}$" title="Please enter 10 digits" />
It's recommended to use the `title` attribute, so users know what the correct value is.
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Phước Nguyễn