The tryWhen
function is a utility function that allows you to retry a function until a condition is met. It takes four
parameters:
fn
: The function to executecondition
: A function that returns a booleanretries
: The number of times to retry the functiondelay
: The delay in milliseconds before the next attempt
Here's the implementation of the tryWhen
function:
export function tryWhen(fn, condition, retries = 3, delay = 1000) {
let attempts = 0;
function attempt() {
if (!condition() && attempts < retries) {
attempts++;
setTimeout(attempt, delay); // Add delay before next attempt
} else if (attempts < retries) {
return fn();
} else {
throw new Error("Condition not met after " + retries + " attempts");
}
}
attempt();
}
Here's an example of how you can use the tryWhen
function to retry a function until a condition is met:
tryWhen(
() => {
console.log("Trying...");
return Math.random();
},
() => {
console.log("Checking...");
return Math.random() > 0.5;
}
);
The tryWhen function can be particularly useful in scenarios where you need to execute a function, but the success of that function depends on certain conditions that might not be met immediately.
For example, consider a scenario where you are building a web application that fetches data from an API. Sometimes, due to network issues or server-side processing, the API might not respond immediately or return the expected data. In such cases, you might want to retry the API call after a certain delay, but only if a specific condition is met (like the network is available or server has finished processing).
The tryWhen
function can be used to implement this retry logic in a clean and concise manner.
tryWhen(
() => fetch('https://api.example.com/data'), // Function to execute (API call)
() => navigator.onLine, // Condition to check (network is available)
5, // Number of retries
2000 // Delay in milliseconds
);
In this example, the fetch function will be retried up to 5 times with a delay of 2 seconds between each attempt, but only if the network is available (navigator.onLine returns true). If the network is not available after 5 attempts, an error will be thrown.
Error Handling
The tryWhen
function throws an error if the condition is not met after the specified number of retries. You can catch
this error and handle it as needed.
try {
tryWhen(
() => fetch('https://api.example.com/data'), // Function to execute (API call)
() => navigator.onLine, // Condition to check (network is available)
5, // Number of retries
2000 // Delay in milliseconds
);
} catch (error) {
console.error("Failed to fetch data:", error.message);
}
In this example, if the network is not available after 5 attempts, the error message "Failed to fetch data: Condition not met after 5 attempts" will be logged to the console.
Return Value
The tryWhen
function returns the result of the function fn
if the condition is met within the specified number of
retries. If the condition is not met after the retries, an error is thrown.
const data = tryWhen(
() => fetch('https://api.example.com/data'), // Function to execute (API call)
() => navigator.onLine, // Condition to check (network is available)
5, // Number of retries
2000 // Delay in milliseconds
);
In this example, the data
variable will contain the result of the API call if the condition is met within 5 retries.
If the condition is not met after 5 retries, an error will be thrown.
Other Approaches
If you need to use this approach for API calls, you might want to consider using a library like Axios, which provides
built-in support for retrying requests with configurable options. However, the tryWhen
function can be useful in
scenarios where you need to retry any function until a condition is met.
There is also a package called retry-axios
that provides a similar functionality for Axios requests. retry-axios
There's also async-retry
which provides a more comprehensive solution for retrying asynchronous functions with
configurable options. async-retry.
There is also Promise.retry
which provides a similar functionality for retrying promises. Promise.retry