Checking input values for special symbols

I am having two text fields in my form. The data to be entered in the field are Name and City respectively开发者_Python百科. I want to check that the user has not entered any special symbols like !,@,#........ i.e, the only thing user should enter must be belonging to a-z,A-Z, though the user can enter Underscore(_), but no numbers, no special symbols.

I want to check this using JavaScript, how can this be achieved.

Thanks in advance.

A classic problem that's usually solved with the help of regular expressions.

var myString = "London";
if (myString.match(/^[a-zA-Z_]+$/)) {
    // Success
}

If you want to allow spaces, like for New York, change the pattern to /^[a-zA-Z_\s]+$/.