We often use javascript to validate Phone Number Fields in web forms. Most of the times, we check if it is a valid number, but sometimes it may be useful to find out the geographical location of the phone number rather than just checking if it's a number! For example, if your website serves people from multiple countries ( which it probably does), wouldn't it be better to know if during the registration process,the user entered a phone number that actually belongs to his/her location?

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