Calling a workflow using web api request in mscrm

function executeWorkflow(accountId, workflowId, clientUrl) {
    var functionName = "executeWorkflow >>";
    var query = "";
    workflowId = "1f5bee55-222e-4741-9318-b3236c88ba02";
    try {

        //Define the query to execute the action
        query = "workflows(" + workflowId.replace("}", "").replace("{", "") + ")/Microsoft.Dynamics.CRM.ExecuteWorkflow";

        var data = {
            "EntityId": accountId//current entity
        };

        //Create request
        // request url
        //https://org.crm.dynamics.com/api/data/v8.2/workflows(“f0ca33cc-23fd-496f-80e1-693873a951ca”)/Microsoft.Dynamics.CRM.ExecuteWorkflow
        var req = new XMLHttpRequest();
        req.open("POST", clientUrl + "/api/data/v8.2/" + query, true);
        req.setRequestHeader("Accept", "application/json");
        req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
        req.setRequestHeader("OData-MaxVersion", "4.0");
        req.setRequestHeader("OData-Version", "4.0");

        req.onreadystatechange = function () {

            if (this.readyState == 4 /* complete */) {
                req.onreadystatechange = null;

                if (this.status == 200) {
                    //success callback this returns null since no return value available.
                    var result = JSON.parse(this.response);


                } else {
                    //error callback
                    var error = JSON.parse(this.response).error;
                }
            }
        };
        req.send(JSON.stringify(data));

    } catch (e) {
        throwError(functionName, e);
    }
}