Benchmark: char index vs charAt() vs slice() vs charCodeAt()

Script Preparation code:

var str = 'foo bar baz';
var noop = Function.prototype;

Tests:

character index
if (str[4] == 'b') noop();
charAt()
if (str.charAt(4) == 'b') noop();
slice()
if (str.slice(4, 5) == 'b') noop();
charCodeAt()
if (str.charCodeAt(4) == 98) noop();

Historical Performance Data aggregated from 13 community runs

Desktop Results:

Chrome 13 runs

charAt()

5.8M/s

charCodeAt()

5.8M/s

character index

5.8M/s

slice()

5.8M/s

View exact numbers

✓ charAt(): 5,838,784 ops/sec
• charCodeAt(): 5,837,962 ops/sec
• character index: 5,820,174 ops/sec
• slice(): 5,811,290 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
character index
charAt()
slice()
charCodeAt()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 15 days ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/150.0.0.0 Safari/537.36 Edg/150.0.0.0

Browser/OS: Chrome 150 on Windows

View result in a separate tab

character index

239.6M/s

charAt()

237.8M/s

charCodeAt()

237.8M/s

slice()

237.3M/s

View exact numbers

Test name	Executions per second
✓ character index	239,559,152 Ops/sec
charAt()	237,822,720 Ops/sec
charCodeAt()	237,781,664 Ops/sec
slice()	237,264,240 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 JSON and explain what's being tested.

**Benchmark Definition**

The benchmark compares four different methods for accessing characters in a string: `char index`, `charAt()`, `slice()`, and `charCodeAt()`.

Here's a brief description of each:

1. **Char Index**: Directly accessing a character at its index using square brackets (`[]`). For example, `str[4]`.
2. **charAt()**: Using the `charAt()` method to get a single character at a specified index. For example, `str.charAt(4)`.
3. **Slice()**: Using the `slice()` method to extract a substring from the original string, starting from the specified index and ending at the next index (exclusive). In this case, `str.slice(4, 5)` is equivalent to getting the single character at index 4.
4. **CharCodeAt()**: Using the `charCodeAt()` method to get the Unicode code point of a single character at a specified index.

**Options Compared**

The benchmark compares these four methods in terms of execution speed (measured in executions per second) across different browsers and devices.

**Pros and Cons of Each Approach**

Here's a brief summary of each approach:

1. **Char Index**: Fast, as it directly accesses the character at the specified index.
	* Pros: Simple, efficient.
	* Cons: May not work for non-string values or indices out of bounds.
2. **charAt()**: Faster than accessing characters by index, but slower than `charCodeAt()`.
	* Pros: More readable, easier to use when dealing with strings.
	* Cons: Slower than direct indexing.
3. **Slice()**: Similar to `charAt()`, but extracts a substring instead of a single character.
	* Pros: Useful for extracting substrings or working with ranges.
	* Cons: Slower than both `charIndex` and `charAt()`.
4. **CharCodeAt()**: Fastest, as it directly accesses the Unicode code point of the character.
	* Pros: Fast, accurate.
	* Cons: Only works for single characters, not substrings or strings.

**Library**

None explicitly mentioned in this benchmark definition. However, some benchmarks might use libraries like Lodash (for `slice()`) or others for specific features or syntax.

**Special JS Feature or Syntax**

No special JavaScript feature or syntax is being used in this benchmark. The examples are straightforward and demonstrate basic string manipulation.

**Alternatives**

Other alternatives for accessing characters in a string include:

1. **String.prototype.at()**: A newer method introduced in ECMAScript 2017, providing similar functionality to `charAt()` but with more features (e.g., handling Unicode code points).
2. **Substr()**: An older method used before `slice()`, which extracts a substring from the original string.
3. Various third-party libraries or utilities for string manipulation.

For this specific benchmark, using a library like Lodash for `slice()` might be unnecessary, as the benchmark is focused on comparing basic string access methods.

char index vs charAt() vs slice() vs charCodeAt() (version: 0)

Compare methods for testing string's character.

Comparing performance of: `character index vs charAt() vs slice() vs charCodeAt()`

Created: one year ago by: Guest

Go to the latest result

character index

charAt()

slice()

charCodeAt()

Historical Performance Data aggregated from 13 community runs

Desktop Results:

Chrome 13 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

char index vs charAt() vs slice() vs charCodeAt() (version: 0)

Compare methods for testing string's character.

Comparing performance of: character index vs charAt() vs slice() vs charCodeAt()

Created: one year ago by: Guest

Go to the latest result

character index

charAt()

slice()

charCodeAt()

Historical Performance Data aggregated from 13 community runs

Desktop Results:

Chrome 13 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: `character index vs charAt() vs slice() vs charCodeAt()`