text-is-lower-case/dist.es2015/index.js

Returns `true` if text is lower case only

/**
 * Returns a boolean indicating whether text is lower case.
 */
export function isLowerCase(input) {
    // Handle null/undefined inputs gracefully
    if (!input)
        return false;
    return input.toLowerCase() === input && input.toUpperCase() !== input;
}