single-load-js.js

let translationsContainer = {

  data : [],
  promise : false,

  load: function() {

    return new Promise((resolve, reject) => {

      if (this.promise) {
        this.promise.then(() => {
          resolve(this.data);
        });
      } else {
        this.promise = Api.get("/api/translations").then((response) => {
          this.data = response.data;
          resolve(this.data);
        });
      }
    });
  }
};

// usage
translationsContainer.load().then((response) => {
  // do things
});