Create Site Columns on Host Web from App Web in SharePoint 2013 using JavaScript

<asp:Content ContentPlaceHolderID="PlaceHolderMain" runat="server">
    <div>
        <input type="button" id="btnSiteColumns" value="Create Site Columns" onclick="createSiteColumns()" />
    </div>
</asp:Content>

Add following code to App.js.

'use strict';

var context = SP.ClientContext.get_current();
var hostWebUrl, hostWebContext, hostWeb;

$(document).ready(function () {
    hostWebUrl = decodeURIComponent(getQueryStringParameter("SPHostUrl"));
    //Get Host Web Context using App web
    hostWebContext = new SP.AppContextSite(context, hostWebUrl);
    hostWeb = hostWebContext.get_web();
});

// Retrieve a query string value.
function getQueryStringParameter(paramToRetrieve) {
    var params = document.URL.split("?")[1].split("&");
    for (var i = 0; i < params.length; i = i + 1) {
        var singleParam = params[i].split("=");
        if (singleParam[0] == paramToRetrieve) return singleParam[1];
    }
}

//Create Site Columns on Host Web
function createSiteColumns() {
    var fields;
    var createFields;
    //Get Host Web Fields Collection
    fields = hostWeb.get_fields();
    //Define the fields schema
    var fieldSchema = new Array(
                     '<Field Name="EmployeeId" DisplayName="Employee ID" Type="Text" EnforceUniqueValues ="TRUE" Indexed="TRUE"  Required="True" Group="EmployeeDetails"/>',
                     '<Field Name="EmployeeName" DisplayName="Employee Name"  Type="User" Required="FALSE" Group="EmployeeDetails"/>');

    for (var iFieldsCounter = 0; iFieldsCounter < fieldSchema.length; iFieldsCounter++) {
        //Parameters to pass
        //fields.addFieldAsXml(string schemaXml,bool addToDefaultView, AddFieldOptions options)
        createFields = fields.addFieldAsXml(fieldSchema[iFieldsCounter], false, SP.AddFieldOptions.addFieldCheckDisplayName);
    }
    context.load(fields);
    context.load(createFields);
    context.executeQueryAsync(
            function () {
                alert('Site Columns Created Successfully.')
            },
            function (sender, args) {
                alert('Failed to create Site Columns. Error:' + args.get_message() + '\n' + args.get_stackTrace());
            });

}