Benchmark: Date.now() loop - MeasureThat.net

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Tests:

Outside loop
const now = Date.now(); const res = []; for(i=0; i<10000; i++){ res.push(now); }
Inside loop
const res = []; for(i=0; i<10000; i++){ res.push(Date.now()); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Outside loop
Inside loop

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) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36

Browser/OS: Chrome 136 on Windows

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Outside loop

4K/s

Inside loop

2K/s

View exact numbers

Test name	Executions per second
✓ Outside loop	3,575 Ops/sec
Inside loop	1,540 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The benchmark "Date.now() loop" tests the performance of two different approaches to collecting timestamps using JavaScript's `Date.now()` method. The aim is to observe the impact on performance when `Date.now()` is invoked once versus multiple times within a loop.

### Options Compared

1. **Outside Loop (Test Name: "Outside loop")**
   - **Benchmark Definition**: 
     ```javascript
     const now = Date.now();
     const res = [];
     
     for(i=0; i<10000; i++){
       res.push(now);
     }
     ```
   - **Description**: Here, `Date.now()` is called once prior to entering the loop, thus capturing the current timestamp. The result is then pushed to an array inside the loop 10,000 times.

2. **Inside Loop (Test Name: "Inside loop")**
   - **Benchmark Definition**: 
     ```javascript
     const res = [];
     
     for(i=0; i<10000; i++){
       res.push(Date.now());
     }
     ```
   - **Description**: In this case, `Date.now()` is called on each iteration of the loop, generating a new timestamp for every entry in the resulting array.

### Performance Results Summary
Based on the benchmark results:
- **Outside loop** yielded approximately **3575.09 executions per second**.
- **Inside loop** yielded approximately **1539.84 executions per second**.

### Pros and Cons of Different Approaches

#### Outside Loop
- **Pros**:
  - Significantly better performance as it eliminates the overhead of repeatedly calling `Date.now()`.
  - Efficient for scenarios where a constant timestamp is needed repeatedly (like logging an event that occurs within a short duration).
  
- **Cons**:
  - If the intention is to collect multiple separate timestamps, this approach won’t suffice, as it only captures one timestamp.

#### Inside Loop
- **Pros**:
  - Useful when you need unique timestamps for every iteration (e.g., measuring time differences or logging events at various intervals).
  
- **Cons**:
  - Substantially slower due to the overhead of repeated function calls within loop iterations—especially when the loop executes many times.
  - Increased computational cost can lead to performance bottlenecks in code that relies on rapid execution of loops.

### Considerations

Choosing between these two approaches often hinges on the specific use case. If you're interested in a single timestamp (like logging), the outside loop method is more optimal. When you need dynamic timestamps (for example, for measuring time-sensitive events across iterations), the inside loop is necessary despite its performance drawbacks.

### Alternatives
1. **Using `performance.now()`**: If higher precision timing is required, `performance.now()` can be used instead of `Date.now()`, which provides timestamp values in milliseconds with sub-millisecond precision. However, similar considerations regarding its invocation frequency will affect performance.

2. **Caching Mechanisms**: In situations where multiple calls to retrieve timestamps with minimal latency are needed, consider implementing a caching strategy to reduce the number of direct calls to these timing functions.

3. **Batch Processing**: If timestamps are used for logging or metrics collection, consider batching the operations where multiple timestamps are needed together to minimize repeated calls.

In conclusion, the test highlights the trade-offs of performance and requirement specificity when working with time-tracking APIs in JavaScript. It serves as an essential guideline for developers when optimizing code involving frequent function calls within loops.

Date.now() loop (version: 1)

Comparing performance of: `Outside loop vs Inside loop`

Created: one year ago by: Guest

Go to the latest result

Outside loop

Inside loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

Date.now() loop (version: 1)

Comparing performance of: Outside loop vs Inside loop

Created: one year ago by: Guest

Go to the latest result

Outside loop

Inside loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

Related benchmarks

Comparing performance of: `Outside loop vs Inside loop`