Update Record in Microsoft Dynamics CRM 2016 using Web API

  function UpdateAccount() {

    var serverURL = Xrm.Page.context.getClientUrl();
    var account = {};
    account["name"] = "Create record Web API Example"; //set single line of text field
    account["address1_city"] = "Islamabad";//set single line of text field
    //Lookup
    account["primarycontactid@odata.bind"] = "/contacts(0D7AFC02-891C-E611-80E1-5065F38B0371)";  //setting existing lookup
    //Below code will create contact on fly and set in primarycontact 
    //account["primarycontactid"] = {
    //    "firstname": "Mahender",
    //    "lastname": "Pal"
    //};

    //optionset
    account["industrycode"] = 1; // set optionSet field
    //two options
    account["donotphone"] = true; //set boolean field
    //number
    account["numberofemployees"] = 20;//set whole no field
    //date time
    //account["him_approvaldate"] = new Date();

    var req = new XMLHttpRequest();
    req.open("PATCH", serverURL + "/api/data/v8.0/accounts(1DD18913-11CB-E511-80D2-C4346BDC11C1)", false);
    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.send(JSON.stringify(account));

    if (req.readyState == 4 /* complete */) {
        if (req.status == 204) {
            
        } else {
            
        }
    }
}