JavaScript String functions (toCamelCase, dasherize, and titleize)

I had the need for a few String functions in JavaScript to manage some variances between data sources so I figured I'd share them.  For example, from one source attributes in the JSON data would use underscores to separate words and in another it would uses dashes (my_attribute vs my-attribute).  Also for simple data display, I wanted to titleize the attribute name for a label (My Attribute). 

/**
 * String.toCamelCase
 *
 * Convert a string to camel case, including hyphens and underscores
 */
String.prototype.toCamelCase = function() {
    return this.replace(/^([A-Z])|[\s-_](\w)/g, function(match, p1, p2, offset) {
        if (p2) return p2.toUpperCase();
        return p1.toLowerCase();        
    });
};

/**
 * String.dasherize
 *
 * Dasherize a string, including periods and underscores
 */
if (!String.prototype.dasherize) {
    String.prototype.dasherize = function() {
        return this.replace(/^([A-Z])|[\s\._](\w)/g, function(match, p1, p2, offset) {
            if (p2) return "-" + p2.toLowerCase();
            return p1.toLowerCase();        
        });
    };
}

/**
 * String.capitalize
 *
 * Capitalize the first letter of a string
 */
if (!String.prototype.capitalize) {
    String.prototype.capitalize = function() {
        return this.charAt(0).toUpperCase() + this.slice(1);
    };
}

/**
 * String.titleize
 *
 * Capitalize the first letter of every word in a string, also separates
 * words by spaces if formally separated by dashes or underscores
 *
 */
if (!String.prototype.titleize) {
    String.prototype.titleize = function() {
        return this.replace(/^([A-Z])|[\s-_](\w)/g, function(match, p1, p2, offset) {
            if (p2) return " " + p2.toUpperCase();
            return p1.toLowerCase();        
        }).capitalize();
    };
}