How to display error based on CRM user's language option using JavaScript

I need to display an error on the CRM form based on the user's language setting. ex: french user - error needs to be displayed in french. How do i get the language(English or French) that the user has set up in the personalization setting in CRM? 

This is where i need to add error message based on the language option

function checkDuplicateTANDForSameOrg (executionContext) {
const formContext = executionContext.getFormContext();

var Entity = "contact";
var Select = "?$select=fullname";
var Filter = "&$filter=contactid eq '3D36A874-49F6-EC11-82E5-002248AE4B85'";

Xrm.WebApi.retrieveMultipleRecords(Entity, Select + Filter).then(
function success(result) {
if (result != null && result.entities.length > 0) {
formContext.ui.clearFormNotification("contactid");
} else{
formContext.ui.setFormNotification("The organization for the selected contact should be same as the organization of the ROD contact.", "ERROR", "contactid");
}

},
function (error) {
console.log(error.message);
}
);

}