Handle-race-condition NPM

handle-race-condition

Module that accepts an async function, and returns an async function that can be called any number of times in parallel, but will always resolve/reject with result of the latest call.

Super simple to use
No dependencies on any other library.
Works with any async function that returns a Promise
Supports AMD

Race condition

There are times when you call an async function multiple times but the ouput may not come in the same order as it was called, i.e, the first call can be resolved after the second call. This is called race condition and you can solve it using this simple module.

How to install

npm i handle-race-condition

Example usage

Consider the example below:

const someAsyncFunction = (time, order) => {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve(order);
        }, time);
    });
};

Here someAsyncFunction is an async function whose output can resolve at different times depending on time. You can think of this time as the time required for an ajax response.

Now lets call this function multiple times:

someAsyncFunction(500, 1).then((order) => { console.log(order) });
someAsyncFunction(200, 2).then((order) => { console.log(order) });
someAsyncFunction(50, 3).then((order) => { console.log(order) });
someAsyncFunction(400, 4).then((order) => { console.log(order) });
someAsyncFunction(100, 5).then((order) => { console.log(order) });

As you can see the output below is not in the same order as it was called:

Now lets use our module:

import handleRaceCondition from 'handleRaceCondition';

const someAsyncFunction = (time, result) => {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve(result);
        }, time);
    });
};

const getResult = handleRaceCondition(someAsyncFunction);

getResult(500, 1).then((result) => { console.log(result) });
getResult(200, 2).then((result) => { console.log(result) });
getResult(50, 3).then((result) => { console.log(result) });
getResult(400, 4).then((result) => { console.log(result) });
getResult(100, 5).then((result) => { console.log(result) });

You pass the desired async function to handleRaceCondition() and it will return another async function which when called multiple times will always resolve for the last call. The output, as you can see now, is resolved when the last call is resolved.