How to Write a Generic findZero Algorithm for Both Sync and Async Functions in JavaScript/TypeScript
Learn how to implement a single generic algorithm in JavaScript/TypeScript that works seamlessly with both synchronous and asynchronous user functions using generator functions.
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This video is based on the question https://stackoverflow.com/q/79461579/ asked by the user 'Niobos' ( https://stackoverflow.com/u/3486486/ ) and on the answer https://stackoverflow.com/a/79461748/ provided by the user 'Bergi' ( https://stackoverflow.com/u/1048572/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.
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Supporting Both Sync and Async Functions in a Generic Algorithm
When writing generic algorithm functions in JavaScript or TypeScript, such as optimization routines, you'll sometimes want them to work with both synchronous and asynchronous user-supplied functions.
For example, consider a simple algorithm to find the first input x where f(x) === 0. A straightforward sync implementation works well with synchronous f, but fails with async functions because it receives a Promise instead of the resolved value.
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You can make an async version easily by using await inside the loop:
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But having two almost identical functions isn't ideal. How can we write one generic algorithm that works with both?
Solution: Use a Generator to Separate Iteration From Evaluation
You can implement your algorithm as a generator function that yields inputs requiring evaluation (f(i)), and receives their results through next() calls. Then, provide two runners:
A synchronous runner that calls the generator and feeds values from a synchronous function
An asynchronous runner that calls the generator and awaits the promise returned by an async function
Step 1: The Generator Algorithm
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This generator produces values i to test and expects the evaluated result to be passed back with next().
Step 2: Synchronous Runner
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This runs the generator synchronously by immediately applying f and passing the result back.
Step 3: Asynchronous Runner
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This runner awaits each promise before passing the resolved value into the generator.
Benefits
Single algorithm logic encapsulated in the generator.
Clear separation of iteration from evaluation.
Flexible integration with sync or async user functions.
Summary
By rewriting your algorithm as a generator function, you can:
Yield evaluation points (inputs)
Receive evaluated results
Run the same algorithm logic both synchronously and asynchronously with minimal duplicated code.
This approach can be generalized easily to more complex iterative algorithms requiring user function calls, preserving code maintainability and flexibility.
Example Usage:
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This pattern provides a clean and powerful technique to unify synchronous and asynchronous workflows in generic algorithm implementations.
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