watch-property.js

/**
 * create a function that will return true once any time the value changes
 * @param {Object} object
 * @param {String} key
 */
 function watchProperty(object, key){

    var value = object[key];

    return function(){
        var changed = value !== object[key];
        if(changed){
            value =object[key];
        }

        return changed;
    };
}

module.exports = exports = watchProperty;



/**
 * watch an array of properties on an object
 * if any of the values have changed return true
 * @returns true if any of the values have changed
 */
exports.any = function some(object, keys){
    var fns = keys.map(function(key){
        return watchProperty(object, key);
    });


    return function(){
        for(var i=0; i<fns.length; i++){
            if( fns[i]() ){
                return true;
            }
        }
        return false;
    };
};


/**
 * watch an array of properties on an object
 * if all of them have changed return true
 * @returns true if all objects have changed value
 */
exports.all = function every(object, keys){

    var fns = keys.map(function(key){
        return watchProperty(object, key);
    });


    return function(){
        for(var i=0; i<fns.length; i++){
            if( !fns[i]() ){
                return false;
            }
        }
        return true;
    };
};