How to Fulfill Sales Order using WebApi

 You can use following code to Fulfill Sales Order using JavaScript and WebApi:

JavaScript

var orderclose = {          var orderclose = { "subject": "null", "salesorderid@odata.bind": "/salesorders(bef45b6f-d1a0-f011-bbd3-7c1e524d7b2a)",//Put salesorder Id here "description": "Additional Description Here", "actualend": new Date() };       var parameters = {         "OrderClose": orderclose,         "Status": -1     };       var context;       if (typeof GetGlobalContext === "function") {         context = GetGlobalContext();     } else {         context = Xrm.Page.context;     }       var req = new XMLHttpRequest();     req.open("POST", context.getClientUrl() + "/api/data/v8.2/salesorders/Microsoft.Dynamics.CRM.FulfillSalesOrder", true);     req.setRequestHeader("OData-MaxVersion", "4.0");     req.setRequestHeader("OData-Version", "4.0");     req.setRequestHeader("Accept", "application/json");     req.setRequestHeader("Content-Type", "application/json; charset=utf-8");     req.onreadystatechange = function () {         if (this.readyState === 4) {             req.onreadystatechange = null;             if (this.status === 204) {                 //Success - No Return Data - Do Something             } else {                 var errorText = this.responseText;                 //Error and errorText variable contains an error - do something with it             }         }     };     req.send(JSON.stringify(parameters));