ChangeCase.js

/**
 *  Our main function has simplied a lot
 */

function changeCase(word, caseType) {

    // We create a map of caseType -> function
    const caseMap = {
        "lower": convertToLower,
        "camel": convertToCamel
    }

    // Look up the caseType "lower", "camel"
    // The map will return its function, call it
    caseType = caseType.trim().toLowerCase();
    var conversionFunction = caseMap[caseType];
    
    // Do we have this conversion function?
    if ( conversionFunction != null )
       return conversionFunction(word);
    else 
       return null;
}