Question 100551 in Javascript Question posted in
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Javascript – Can I make a closure of an async function to pass as a promise

I have a somedataMap : Map<string, Promise<SomeData>> that I would like to populate.

I also have an async function async function getSomeData(someIdentifier:string): Promise<SomeData>, that I would like use as the values in that map

Obviously if I do something like somedataMap.set("someId", getSomeData("someId")), then the code in getSomeData is called, which I don’t want to do until maybe later. What is the best way to wrap/closure the getSomeData function as a Promise so I can store it or pass it to other functions?

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2

Answers


  1. 0

    You can use either

    somedataMap: Map<string, () => Promise<SomeData>>

somedataMap.set("someId", () => getSomeData("someId"))

    OR

    use it as it is, and later, when you want to receive value from Promise, do the following:

    await somedataMap.get("someId")
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  2. 0

    Async functions always return promises. You don’t need to wrap it. Just call it.

    const getSomeData = async (id) => {
  return 'some data';
};

const somedataMap = new Map();

getSomeData('x').then(data => {

  console.log(`data is "${data}"`);

  somedataMap.set("someId", data);

  console.log( somedataMap.values().next().value );

});
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