[Decamelize] Decamelizes a string with/without a custom separator (underscore by default) #javascript #camelcase #utility

decamelize.js

/**
 * Decamelizes a string with/without a custom separator (underscore by default).
 * 
 * @param str String in camelcase
 * @param separator Separator for the new decamelized string.
 */
function decamelize(str, separator){
	separator = typeof separator === 'undefined' ? '_' : separator;

	return str
        .replace(/([a-z\d])([A-Z])/g, '$1' + separator + '$2')
        .replace(/([A-Z]+)([A-Z][a-z\d]+)/g, '$1' + separator + '$2')
        .toLowerCase();
}