Deep Extend underscore typescrpit

gistfile1.txt

  import * as _ from "underscore";

/**
 * @param destination
 * @param sources
 * @returns {any}
 * @constructor
 */
export function DeepExtend (destination: any, ...sources: any[]): any {
    var parentRE: RegExp = new RegExp('#{\s*?_\s*?}');

    _.each(sources, function(source: any) {
        for (let prop in source) {
            if (!source.hasOwnProperty(prop)) {
                continue;
            }

            if (_.isUndefined(destination[prop]) || _.isFunction(destination[prop]) || _.isNull(source[prop]) || _.isDate(source[prop])) {
                destination[prop] = source[prop];
            } else if (_.isString(source[prop]) && parentRE.test(source[prop])) {
                if (_.isString(destination[prop])) {
                    destination[prop] = source[prop].replace(parentRE, destination[prop]);
                }
            } else if (_.isArray(destination[prop]) || _.isArray(source[prop])){
                if (!_.isArray(destination[prop]) || !_.isArray(source[prop])){
                    throw new Error('Trying to combine an array with a non-array (' + prop + ')');
                } else {
                    destination[prop] = _.reject(DeepExtend(_.clone(destination[prop]), source[prop]), function (item) { return _.isNull(item);});
                }
            } else if (_.isObject(destination[prop]) || _.isObject(source[prop])){
                if (!_.isObject(destination[prop]) || !_.isObject(source[prop])){
                    throw new Error('Trying to combine an object with a non-object (' + prop + ')');
                } else {
                    destination[prop] = DeepExtend(_.clone(destination[prop]), source[prop]);
                }
            } else {
                destination[prop] = source[prop];
            }
        }
    });

    return destination;
}