Query Metadata of Global OptionSet in Microsoft Dynamics CRM 2016 using Web API

To retrieve meta data of global optionSet in Web API, first you will need to retrieve  meta data id of option Set.
So i create two functions , 

RetrieveGlobalOptionSetMetaDataId("OptionSetSchemaName") function 

will retrieve meta data id of optionSet by passing schema name of option , then pass meta data id to

RetrieveGlobalOptionSetOptionsMetaData(optionSetMetaDataId) 

it will retrieve meta data of optionSet.

I am binding options of global optionSet to Select element in Html Page , 

var globalOptionSetMetaDataId = RetrieveGlobalOptionSetMetaDataId("OptionSetSchemaName");



RetrieveGlobalOptionSetOptionsMetaData(globalOptionSetMetaDataId );





function RetrieveGlobalOptionSetMetaDataId(OptionSetSchemaName) {



    var globalOptionSetMetaDataId = null;

    var context = parent.Xrm.Page.context;

    var webapiQuery = context.getClientUrl() + "/api/data/v8.0/GlobalOptionSetDefinitions?$select=Name";

    var service = new XMLHttpRequest();

    service.open("GET", webapiQuery, false);

    service.setRequestHeader("Accept", "application/json");

    service.setRequestHeader("Content-Type", "application/json; charset=utf-8");

    service.setRequestHeader("OData-MaxVersion", "4.0");

    service.setRequestHeader("OData-Version", "4.0");

    service.send();

    if (service.readyState == 4 /* complete */) {

        if (service.status == 201 || service.status == 200) {

            var RetrieveService = eval('(' + service.responseText + ')');

            if (RetrieveService.value.length > 0) {

                for (var i = 0; i < RetrieveService.value.length; i++) {

                    if (RetrieveService.value[i].Name == OptionSetSchemaName) {

                        globalOptionSetMetaDataId = RetrieveService.value[i].MetadataId;

                        break;

                    }

                }

            }

        }

    }

    return globalOptionSetMetaDataId ;

}





function RetrieveGlobalOptionSetOptionsMetaData(optionSetMetaDataId) {



    var context = parent.Xrm.Page.context;

    var webapiQuery = context.getClientUrl() + "/api/data/v8.0/GlobalOptionSetDefinitions(" + optionSetMetaDataId + ")";

    var service = new XMLHttpRequest();

    service.open("GET", webapiQuery, false);

    service.setRequestHeader("Accept", "application/json");

    service.setRequestHeader("Content-Type", "application/json; charset=utf-8");

    service.setRequestHeader("OData-MaxVersion", "4.0");

    service.setRequestHeader("OData-Version", "4.0");

    service.send();

    if (service.readyState == 4 /* complete */) {

        if (service.status == 201 || service.status == 200) {

            var RetrieveService = eval('(' + service.responseText + ')');

            if (RetrieveService.Options.length > 0) {

                var options = "";

                for (var i = 0; i < RetrieveService.Options.length; i++) {

                    var optionLabel = RetrieveService.Options[i].Label.UserLocalizedLabel.Label;

                    var optionValue = RetrieveService.Options[i].Value;

                    options += "<option value='" + optionValue + "'>" + optionLabel + "</option>";

                }

                $("#dropdownReason").html(options);

            }

        }

    }

}