Benchmark: Different types of selecting

Different types of selecting (version: 0)

Comparing performance of: getElementById vs querySelector("#id") vs getElementsByClassName("class")[0] vs querySelector(".class") vs getElementById + getElementsByTagName vs querySelectorAll("#id tag") vs getElementById + getElementsByClassName[0] vs querySelector("#id .class") vs getElementsByClassName("class") vs querySelectorAll(".class")

Created: 7 years ago by: Guest

Jump to the latest result

HTML Preparation code:

<div>
  <ul id="id1">
    <li class="c1">Element</li>
    <li id="id2" class="c1">Element</li>
    <li class="c1">Element</li>
    <li class="c1">Element</li>
  </ul>
</div>

Tests:

getElementById
document.getElementById("id2")
querySelector("#id")
document.querySelector("#id2")
getElementsByClassName("class")[0]
document.getElementsByClassName("c1")[0]
querySelector(".class")
document.querySelector(".c1")
getElementById + getElementsByTagName
document.getElementById("id1").getElementsByTagName("li")
querySelectorAll("#id tag")
document.querySelectorAll("#id1 li")
getElementById + getElementsByClassName[0]
document.getElementById("id1").getElementsByClassName("c1")[0]
querySelector("#id .class")
document.querySelector("#id1 .c1")
getElementsByClassName("class")
document.getElementsByClassName("c1")
querySelectorAll(".class")
document.querySelectorAll(".c1")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
querySelector("#id")
getElementsByClassName("class")[0]
querySelector(".class")
getElementById + getElementsByTagName
querySelectorAll("#id tag")
getElementById + getElementsByClassName[0]
querySelector("#id .class")
getElementsByClassName("class")
querySelectorAll(".class")

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Measuring JavaScript performance is crucial for understanding the efficiency of different approaches to DOM manipulation.

The provided JSON represents a benchmark test with eight individual test cases, each measuring the performance of different methods for selecting elements in an HTML document. The test cases are:

1. `document.getElementById("id2")`
2. `document.querySelector("#id2")`
3. `document.getElementsByClassName("c1")[0]`
4. `document.querySelector(".c1")`
5. `document.getElementById("id1").getElementsByTagName("li")`
6. `document.querySelectorAll("#id1 li")`
7. `document.getElementById("id1").getElementsByClassName("c1")[0]`
8. `document.querySelector("#id1 .c1")`

These test cases cover various scenarios, including:

* Using an ID to select an element (`getElementById`)
* Using a CSS selector to select an element (`querySelector` or `getElementsByClassName`)
* Combining multiple selectors (`querySelectorAll` with a tag and class)
* Using the `getElementsByTagName` method
* Using the `getElementsByClassName` method

Now, let's analyze the pros and cons of each approach:

**1. `document.getElementById("id2")`**

Pros: Simple, reliable, and widely supported.
Cons: Can be slow if the element is not found, as it requires a DOM search.

**2. `document.querySelector("#id2")`**

Pros: More efficient than `getElementById`, as it returns multiple elements if present in the DOM.
Cons: May return unexpected results if the CSS selector is ambiguous or incorrect.

**3. `document.getElementsByClassName("c1")[0]`**

Pros: Efficient, as it uses a single method call and returns only one element.
Cons: May not work if the class name is not unique (returns all elements with that class).

**4. `document.querySelector(".c1")`**

Pros: Similar to `getElementsByClassName`, but more concise and readable.
Cons: May return unexpected results if the CSS selector is ambiguous or incorrect.

**5. `document.getElementById("id1").getElementsByTagName("li")`**

Pros: Efficient, as it uses a single method call and returns all matching elements in one step.
Cons: Returns a HTMLCollection, which may not be as readable as an array of elements.

**6. `document.querySelectorAll("#id1 li")`**

Pros: More efficient than `getElementsByClassName`, as it returns all matching elements at once.
Cons: May return unexpected results if the CSS selector is ambiguous or incorrect.

**7. `document.getElementById("id1").getElementsByClassName("c1")[0]`**

Pros: Similar to `getElementsByClassName`, but uses a single method call and returns only one element.
Cons: May not work if the class name is not unique (returns all elements with that class).

**8. `document.querySelector("#id1 .c1")`**

Pros: Efficient, as it uses a single method call and returns only one element.
Cons: May return unexpected results if the CSS selector is ambiguous or incorrect.

In general, using CSS selectors (`querySelector` or `getElementsByClassName`) can be more efficient than relying on ID-based selection (`getElementById`). However, the performance difference may not be significant in all cases, especially when dealing with complex HTML documents. The best approach ultimately depends on the specific use case and personal preference.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.102 Safari/537.36

Browser/OS: Chrome 85 on Mac OS X 10.15.6

View result in a separate tab

Test name	Executions per second
getElementById	2695774.2 Ops/sec
querySelector("#id")	1581612.5 Ops/sec
getElementsByClassName("class")[0]	2041642.0 Ops/sec
querySelector(".class")	2171591.5 Ops/sec
getElementById + getElementsByTagName	1937806.2 Ops/sec
querySelectorAll("#id tag")	757438.5 Ops/sec
getElementById + getElementsByClassName[0]	1752573.8 Ops/sec
querySelector("#id .class")	2350441.5 Ops/sec
getElementsByClassName("class")	2510279.8 Ops/sec
querySelectorAll(".class")	798654.8 Ops/sec

Related benchmarks:

Different types of selecting (version: 0)

Created: 7 years ago by: Guest

Jump to the latest result

getElementById

querySelector("#id")

getElementsByClassName("class")[0]

querySelector(".class")

getElementById + getElementsByTagName

querySelectorAll("#id tag")

getElementById + getElementsByClassName[0]

querySelector("#id .class")

getElementsByClassName("class")

querySelectorAll(".class")

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):