Benchmark: Await vs Then - MeasureThat.net

Script Preparation code:

function foo(i) {
  return Promise.resolve(i+1);
}

function recur(i) {
  return i >= 10 ? Promise.resolve(i) : foo(i).then(recur);
}

function testThen() {
  return foo(0).then(recur);
}

async function testAwait() {
  let i = await foo(0);
  while (i < 10) {
    i = await foo(i);
  }
  
  return i;
}

Tests:

Then
testThen()
Await
testAwait();

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

Then

2.1M/s

Await

1.7M/s

Fastest: Then (1.2x faster)

View exact numbers

✓ Then: 2,085,611 ops/sec
• Await: 1,682,751 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Then
Await

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:135.0) Gecko/20100101 Firefox/135.0

Browser/OS: Firefox 135 on Windows

View result in a separate tab

Then

1.0M/s

Await

823K/s

View exact numbers

Test name	Executions per second
✓ Then	1,032,057 Ops/sec
Await	823,169 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its test cases to understand what's being compared.

**Benchmark Definition**

The provided JSON represents a JavaScript microbenchmark that compares two approaches for handling asynchronous operations: `then` vs `await`. The script, stored in the `"Script Preparation Code"` section, defines two functions:

1. `foo(i)`: Returns a promise that resolves with `i+1`.
2. `recur(i)`: A recursive function that returns a promise that resolves when `i` reaches 10. It calls itself recursively until the condition is met.

The benchmark creates two test functions:

1. `testThen()`: Calls `foo(0)` and then calls `recur()` on the returned promise.
2. `testAwait()`: Waits for the result of `foo(0)` using `await` and then calls `recur()` on the returned promise.

**Options Compared**

The benchmark compares two approaches:

1. **Then**: Uses `.then()` to chain promises together, waiting for each promise to resolve before proceeding.
2. **Await**: Uses the `await` keyword to wait for promises to resolve directly in the code.

**Pros and Cons of Each Approach**

**Then:**

Pros:

* More explicit control over promise chaining
* Can be more efficient when dealing with a large number of nested promises

Cons:

* Can lead to callback hell (nested `.then()` calls) if not managed carefully
* May result in slower performance due to the overhead of waiting for each promise to resolve

**Await:**

Pros:

* Simplifies asynchronous code by allowing `await` to wait for promises directly
* Reduces the risk of callback hell compared to using `.then()`

Cons:

* Can lead to slower performance if not optimized correctly (e.g., avoiding unnecessary await statements)
* Requires a compatible JavaScript engine that supports the `async/await` syntax

**Library and Syntax**

The benchmark uses the following library:

* None explicitly mentioned, but it's likely using built-in JavaScript features like Promises and async/await.

No special JavaScript features or syntax are used in this benchmark. The focus is on comparing two approaches for handling asynchronous operations.

**Other Alternatives**

If you were to design an alternative benchmark, you might consider adding more test cases or variations, such as:

* Using `async/await` with a library like `bluebird` that provides a more efficient promise implementation
* Adding tests for handling errors and edge cases (e.g., promises rejected early)
* Comparing the performance of different types of asynchronous operations (e.g., callbacks, promises, async functions)

The provided benchmark is a good starting point for understanding the trade-offs between `then` and `await`, but you could expand on it to cover more scenarios and explore additional optimization techniques.

Await vs Then (version: 0)

Comparing performance of: `Then vs Await`

Created: 4 years ago by: Guest

Go to the latest result

Then

Await

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Await vs Then (version: 0)

Comparing performance of: Then vs Await

Created: 4 years ago by: Guest

Go to the latest result

Then

Await

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Related benchmarks

Comparing performance of: `Then vs Await`