Regex for names validation allow only letters and spaces

Question

I'm trying to validate using jQuery Validator if input only contains spaces, and allow space only if there's a letter inside it.

Note that it should also display error if name contains numbers. Allow only the space if it starts with a letter.

This is what I have so far that only allows letters and spaces:

jQuery.validator.addMethod("letterswithspace", function(value, element) {
    return this.optional(element) || /^[a-z\s]+$/i.test(value);
}, "letters only");

Also tried this one but it trims the string and can't add a space between names:

first_name : {
    letterswithspace : true,
     required: {
         depends:function(){
             $(this).val($.trim($(this).val()));
             return true;
         }
     }
 }

Answer 1

To match the terms:

• Expression can start only with a letter
• Expression can contain letters or spaces

You need to use this regex expression:

/^[a-z][a-z\s]*$/

So in your js it should be:

jQuery.validator.addMethod("letterswithspace", function(value, element) {
    return this.optional(element) || /^[a-z][a-z\s]*$/i.test(value);
}, "letters only");

Explanation

1. ^[a-z] means start with one letter
2. [a-z\s]*$ means after accept zero or more letters or spaces

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Valid sentence

If you want a valid sentence structure:

• Expression can start or end only with a letter
• Expression cannot contain consecutive spaces

use:

/^([a-z]+\s)*[a-z]+$/

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By the way

2. These regex expressions do not accept capital letters. To add capital letters support instead of a-z use a-zA-Z