The art of patience: A guide to waiting for a TypeScript/JavaScript promise to resolve before delivering

As a beginner in posting on forums, I'm hoping this one goes smoothly. I've been working with promises for three hours now and still can't seem to grasp them. Unfortunately, Async Wait is not supported in our project and I'm currently using pouchdb over sqlite.

The issue I'm facing is with the display of recipes on my page. Initially, it returns empty and then lags behind by one recipe each time a new one is added. I suspect this is due to returning this.recipeBook before all promises are completed. Although in the code I shared, the final return statement is placed outside any promise, when I try putting it inside a promise, I encounter a "type void is not assignable to type any[]" error in RecipesPage.ts.

I would greatly appreciate any guidance or support you can provide in helping me understand the correct way to handle this situation. Thank you in advance!

This is the call in RecipesPage.ts:

this.recipes = this.database.getAllRecipes();

And here is the method in database.service.ts:

public getAllRecipes() {
this.recipeBook = new Array<Recipe>();

this.recipeDatabase.allDocs
({
  include_docs: true,
}).then(docs => {
  this.objectArray = docs.rows.map(row => {
    return row.doc;
  })
}).then(() => {
  for (let object of this.objectArray) {
    this.myRecipe = this.convertObjectToRecipe(object);
    this.recipeBook.push(this.myRecipe);
  }
})
return this.recipeBook;
}

Answer №1

Unpacking a promise in this scenario is not feasible. The best approach is to utilize polling methods to check for the promise's resolution.

Instead of unpacking the promise, it's recommended to return the promise and use .then to handle its fulfillment. This mirrors the functionality of async and await behind the scenes. Prioritize rendering decisions in the UI based on whether content has been loaded or is currently loading.

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