How to wait for a JSONModel.loadData() request in UI5

Using synchronous ajax requests is not recommended as it blocks the UI and will probably result in a warning in the console.

You can attach to the Model.requestCompleted event to access the asynchronously loaded data:

oModel.attachRequestCompleted(function() {
        console.log(oModel.getData());
    });

The keyword you are looking for is "Deferred"-object --> it enables you to wait for an AJAX request in SAPUI5.

Check this for SAPUI5 context: SAPUI5 Wait for an Deferred-Object // wait for .done() function

Since UI5 version 1.64.0, the API loadData returns a Promise instance:

logLoadedData: async function () {
  const jsonModel = new JSONModel();
  await jsonModel.loadData("<host>/data/config.json");
  console.log(jsonModel.getData()); // after the loadData promise is resolved
},

Alternatively, there is also the API dataLoaded which returns a promise as well. It will resolve when all requests sent by loadData are finished. Here is a syntax without async-await:

doSomethingWith: async function (jsonModel) {
  // Not sure if the model has all data loaded? Just use dataLoaded:
  await jsonModel.dataLoaded();
  console.log(jsonModel.getData());
},

The API loadData is also called internally when the constructor function of JSONModel was called with a string (URL) as an argument. In that case, dataLoaded might come in handy as well.