If you need to get Object Type Code of entity based on Logical Name of entity you can use following code:
var entityLogicalName = "account"; var requestUrl = "/api/data/v8.2/EntityDefinitions?$filter=LogicalName eq '" + entityLogicalName + "'&$select=ObjectTypeCode"; var context; if (typeof GetGlobalContext === "function") { context = GetGlobalContext(); } else { context = Xrm.Page.context; } var req = new XMLHttpRequest(); req.open("GET", context.getClientUrl() + requestUrl, 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 === 200) { var result = JSON.parse(this.response); var objectTypeCode = result.value[0].ObjectTypeCode; //use retrieved objectTypeCode } else { var errorText = this.responseText; //handle error here } } }; req.send();