Regular expression not to accept 2 whitespaces and special characters

Question

I have a problem creating a regular expression:

1. I have to validate that a string does not accept two or more blanks.
   Example: ABCabc aasbdfdf% $ && $$ / $ /

2. If the user types a string as the above example shows a modal " Not a valid name ":

This is my code:

 var newexprg = /^(?!\s*$)[-a-zA-Z0-9_:,.' ']{1,100}$/;
    var obj= {
        descripcion: des,<--- 'ABCabc   $%/##%%aass'
        nombre: $("#txtNombre").val(), <--- 'ABCabc   $%/##%%aass'
    }
    if (newexprg.test(obj.nombre)) {
        if (newexprg.test(obj.descripcion)) {

            $('#modal-Caracteres').modal("show");
        } else {
            $.ajax({
                type: "POST",
                url: 'MyMethodSave',
                contentType: "application/json;charset=utf-8",
                dataType: "json",
                data: "{ParameterName:" + JSON.stringify(obj) + "}",
                async: false,
                success: function (response) {

                },
            });
        }
    } else {
        $('#modal-Caracteres').modal("show");
    }

But every time I enter my chain such method saves the object.

Answer 1

A RegEx to match with a negative condition, such as " it does not contain 2 whitespaces " is possible, but there's a much easier approach to this:

Match a string with with 2 whitespaces:

/\s\S*\s/

• Matches: a whitespace \\s followed by any number of characters that are not whitespace \\S* and followed by a second whitespace \\s .

And then negate the value returned by the match:

var newexprg = /\s\S*\s/;

if (! /\s\S*\s/.test(yourString)) {
    // Valid
} else {
    // Invalid
}