Benchmark: .substr vs .startwith

HTML Preparation code:

<div></div>

Script Preparation code:

window.regex = /^QG/;
window.match = 'test';
var data = window.data = [];
const possible = "0123456789QTPG";
var TOTAL_STRINGS = window.TOTAL_STRINGS = 100000;

function getRandomInt(max) {
  return Math.floor(Math.random() * max);
}

function makeRandomString(len) {
  var text = "";
  for( var i=0; i < len; i++ ) {
    text += possible.charAt(getRandomInt(possible.length));
  }
  return text;
}

while (data.length < TOTAL_STRINGS) {
  data.push(makeRandomString(getRandomInt(10)));
}

Tests:

startsWith
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; while (x < TOTAL_STRINGS) { const str = data[x]; str.startsWith("QG"); x += 1; }
substr
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var match = window.match; while (x < TOTAL_STRINGS) { const str = data[x]; str.substr(0,2)=="QG" x += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
substr

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.2:3b, generated 11 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its components.

**Benchmark Overview**

The benchmark compares two string comparison methods: `substr` and `startsWith`. The goal is to determine which method is faster.

**Script Preparation Code**

The script preparation code sets up a few variables:

1. `window.regex`: defines a regular expression (`/^QG/`) that matches the string "QG".
2. `window.match`: assigns the value "test" to this variable.
3. Creates an array `data` with 100,000 random strings (generated using `makeRandomString(len)`).
4. Defines a helper function `getRandomInt(max)` for generating random integers.

**Html Preparation Code**

The HTML preparation code is empty, as this benchmark only tests JavaScript code.

**Individual Test Cases**

There are two test cases:

1. **startsWith**: uses the `startsWith` method to check if each string in the `data` array starts with "QG".
2. **substr**: uses the `substr` method (with a fixed length of 2) to check if each string in the `data` array contains "QG" as its first two characters.

**Library and Special JS Features**

There is no explicit mention of any libraries, but `window.regex` suggests that this benchmark might use regular expressions. However, without more context or a deeper understanding of the script, it's difficult to confirm this.

**Pros and Cons of Different Approaches**

1. **startsWith**:
	* Pros: more readable and efficient for exact matching.
	* Cons: may be slower if not implemented correctly (e.g., using `indexOf` instead of `startsWith`).
2. **substr**:
	* Pros: can be faster if optimized correctly, especially when the substring length is fixed.
	* Cons: less readable and might require more CPU cycles to compute the index.

**Other Considerations**

When evaluating these test cases, keep in mind that:

1. The benchmark measures the number of executions per second (ExecutionsPerSecond), which indicates how many iterations can be completed within a given time frame.
2. The results may vary depending on factors like JavaScript engine, browser version, and system resources.

**Alternatives**

Other string comparison methods you might consider testing in a similar benchmark include:

1. `indexOf()`
2. `includes()` (introduced in ECMAScript 2015)
3. Regular expression matching (`/regex/`)

To make the benchmark more comprehensive, you could also explore additional factors, such as:

1. String length and complexity
2. Unicode support and compatibility
3. Performance variations across different browser engines

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36 OPR/76.0.4017.123

Browser/OS: Opera 76 on Windows

View result in a separate tab

Test name	Executions per second
startsWith	862.6 Ops/sec
substr	3059.8 Ops/sec

Related benchmarks:

.substr vs .startwith (version: 0)

Testing some things

Comparing performance of: startsWith vs substr

Created: 3 years ago by: Guest

Jump to the latest result

startsWith

substr

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.2:3b, generated 11 days ago):