JavaScript Promise Complete Reference

JavaScript Promises are used to handle asynchronous operations JavaScript. They are easy to manage when dealing with multiple asynchronous operations where callbacks can create callback hell leading to unmanageable code. Promises are the ideal choice for handling asynchronous operations in the simplest manner. They can handle multiple asynchronous operations easily and provide better error handling than callbacks and events.

Syntax

Promise.function();

Example:

Javascript

<script>
    // Illustration of Promise.allSettled()
    // Method in Javascript with Example

    const p1 = Promise.resolve(50);
    const p2 = new Promise((resolve, reject) =>
                    setTimeout(reject, 100, 'geek'));
    const prm = [p1, p2];

    Promise.allSettled(prm).
      then((results) => results.forEach((result) =>
      console.log(result.status,result.value)));
</script>

Output:

"fulfilled"
50
"rejected" 
undefined

The complete list of JavaScript Promise are listed below:

JavaScript Promise Static Methods:

Static methods	Description
all()	Handle all the asynchronous operations), that take an array of promises(an iterable) as input.
allSettled()	Get a promise when all inputs are settled that is either fulfilled or rejected.
race()	Returns a single Promise after receiving an iterable of promises as input.
resolve()	Returns a Promise object that is resolved with a given value.

JavaScript PromiseInstance Methods:

Instance method	Description
then()	Deal with asynchronous tasks such as an API call.

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