Question

I have a function in which I am first checking that a string passed as argument has letters only or not. But it always return as false. Below is my jsfiddle

function takeString (str) {
    var regex = "/^[A-Za-z]+$/";

    if (str.match(regex)) {
        if (str.charCodeAt(0) === str.toUpperCase().charCodeAt(0)) {
            alert('true');
            return true;
        } 
        else {
            alert('false');
            return false;
        }
    } 
    else {
        alert('Only letters please.');
    }
}

takeString('string');

​
The above code always alerts Only letters please.

Answer 1

You need to get rid of the quotes to make regex a regular expression literal:

var regex = /^[A-Za-z]+$/;

Here’s an updated fiddle.

Currently, regex refers to a string literal. When you pass something that’s not a regular expression object or literal to String#match, it implicitly converts that argument to a regular expression object (see ES5 15.5.4.10):

• If Type(regexp) is Object and the value of the [[Class]] internal property of regexp is "RegExp", then let rx be regexp;
• Else, let rx be a new RegExp object created as if by the expression new RegExp( regexp) where RegExp is the standard built-in constructor with that name.

Your regular expression is therefore interpreted like this (since the string contains the forward slash characters you were expecting to delimit a regular expression literal):

var regex = /\/^[A-Za-z]+$\//;

That can’t match anything, since it’s looking for a forward slash, followed by the start of the string.