Benchmark: toFixed vs toPrecision vs Math.round() vs Math.floorfast vs MDN round_to_precision

toFixed vs toPrecision vs Math.round() vs Math.floorfast vs MDN round_to_precision (version: 0)

Added MDN round to precision function: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/round

Comparing performance of: toFixed(4) vs toPrecision(4).toString() vs (Math.round(*10000)/10000).toString() vs Math.floor fast vs precisition round

Created: 6 years ago by: Guest

Jump to the latest result

Script Preparation code:

var someFloat = 0.123456789;
 var round_to_precision = function (x, precision) {
    var y = +x + (precision === undefined ? 0.5 : precision/2);
    return y - (y % (precision === undefined ? 1 : +precision));
};

Tests:

toFixed(4)
someFloat.toFixed(4);
toPrecision(4).toString()
someFloat.toPrecision(4);
(Math.round(*10000)/10000).toString()
(Math.round(someFloat*10000)/10000);
Math.floor fast
~~(someFloat * 10000) / 10000;
precisition round
round_to_precision(someFloat, 4);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
toFixed(4)
toPrecision(4).toString()
(Math.round(*10000)/10000).toString()
Math.floor fast
precisition round

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:144.0) Gecko/20100101 Firefox/144.0

Browser/OS: Firefox 144 on Linux

View result in a separate tab

Test name	Executions per second
toFixed(4)	13354571.0 Ops/sec
toPrecision(4).toString()	9280721.0 Ops/sec
(Math.round(*10000)/10000).toString()	787530688.0 Ops/sec
Math.floor fast	777832256.0 Ops/sec
precisition round	748847936.0 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 provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares the performance of five different methods to round or format a floating-point number: `toFixed`, `toPrecision`, `Math.round()`, `Math.floorfast` (a faster version of `Math.floor()`), and an MDN-specific function called `round_to_precision`.

**Options Compared**

Here's a brief overview of each option being compared:

1. **`toFixed(4)`**: Rounds the number to four decimal places.
2. **`toPrecision(4).toString()`**: Rounds the number to four decimal places using the `toPrecision()` method, which is then converted to a string.
3. **`(Math.round(*10000)/10000).toString()`**: Rounds the number by multiplying it by 10,000, rounding the result to the nearest integer using `Math.round()`, and then dividing by 10,000.
4. **`~~(someFloat * 10000) / 10000;`**: Uses a bitwise operation (`~`) to round the number to four decimal places. This method is often referred to as "integer division" or "flooring" in JavaScript.
5. **`round_to_precision(someFloat, 4);`**: Uses an MDN-specific function called `round_to_precision()` to round the number to four decimal places.

**Pros and Cons of Each Approach**

Here's a brief summary of the pros and cons of each approach:

1. **`toFixed(4)`**: Pros: Simple, widely supported. Cons: May not be suitable for very large numbers or certain edge cases.
2. **`toPrecision(4).toString()`**: Pros: More flexible than `toFixed()`, but still simple. Cons: May be slower due to the extra conversion step.
3. **`(Math.round(*10000)/10000).toString()`**: Pros: Fast and efficient, but may be less intuitive for some developers. Cons: Requires explicit multiplication by 10,000.
4. **`~~(someFloat * 10000) / 10000;`**: Pros: Extremely fast and lightweight, as it only requires a simple arithmetic operation. Cons: May not work correctly for negative numbers or very large values.
5. **`round_to_precision(someFloat, 4);`**: Pros: Specifically designed to round floating-point numbers, with an optional precision argument. Cons: Only supported in certain browsers and versions.

**Library and Syntax**

The `round_to_precision()` function is a custom implementation provided by the benchmark author. It's not part of the standard JavaScript library and may not be supported in all browsers or environments.

**Special JS Feature or Syntax**

There are no special features or syntaxes being tested in this benchmark, other than the use of bitwise operations (`~`) in option 4.

Now that we've broken down the benchmark, let's consider some alternative approaches:

* **Using `Number.EPSILON`**: Instead of using a fixed precision value (e.g., 4), you could use `Number.EPSILON`, which is the smallest positive difference between two numbers with the same significant digits.
* **Using a library like `Mathjs` or `Big.js`**: These libraries provide more advanced mathematical functions and tools that might be useful for certain types of rounding or formatting tasks.

I hope this explanation helps!

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