Javascript: Async/Await

"async and await make promises easier to write"

async makes a function return a Promise

await makes a function wait for a Promise

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Async Syntax

The keyword async before a function makes the function return a promise:

async function myFunction() {

    // "Producing Code" (May take some time)

    return "Hello World"

}

Here is how to use the Promise:

// "Consuming Code" (Must wait for a fulfilled Promise)
myFunction().then(

    function( success ) { 

        /* code if successful */ 
        console.log( success )

    },

    function( error ) { 

        /* code if some error */ 
        console.error( error )

    }

)

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Example

1

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2 Display

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Await Syntax

The await keyword can only be used inside an async function.

The await keyword makes the function pause the execution and wait for a resolved promise before it continues:

let value = await promise

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Example

1

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2 Display

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3 Waiting for a file

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4 Waiting for a file - return

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Async Function (developer.mozilla.org)

The async function declaration declares an async function where the await keyword is permitted within the function body. The async and await keywords enable asynchronous, promise-based behavior to be written in a cleaner style, avoiding the need to explicitly configure promise chains.

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