This benchmark on MeasureThat.net evaluates various approaches for applying CSS styles to a DOM element in JavaScript. Specifically, it compares six different methods for changing the styles of an HTML element repeatedly within a loop of 10,000 iterations. Each method is tested to determine how performant it is in terms of executions per second.

Methods Compared

1. style.setProperty

   • Description: This method sets a CSS property on an element’s style object by specifying the property name and value.
   • Pros:
     • More granular control—allows you to change individual CSS variables or properties.
     • Can be used for setting custom properties (CSS variables).
   • Cons:
     • Potentially slower than other mass assignment methods when multiple properties need updating.

2. style.cssText

   • Description: This method is a string representation of the element's inline CSS. By setting cssText, you can override all the styles of the element.
   • Pros:
     • Fast for setting multiple properties at once—overwrites all existing inline styles with a single string.
   • Cons:
     • Risk of losing existing styles unintentionally since it replaces all current styles.

3. style (direct assignment)

   • Description: The style property can be assigned an object-like string similar to cssText.
   • Pros:
     • Simple to understand and read.
   • Cons:
     • Similar to cssText, but lacks the performance due to repeated reassignment of the style object as a whole.

4. Object.assign

   • Description: This method copies the properties of a JavaScript object and applies them to the element’s style property.
   • Pros:
     • Extensive flexibility, allowing for bulk property assignment and maintaining existing styles.
   • Cons:
     • Can be slower for direct style manipulation compared to methods like setProperty or cssText.

5. setAttribute

   • Description: This method sets an HTML attribute on an element. Here, it’s used to set the 'style' attribute directly as a string.
   • Pros:
     • Works universally across all attributes. Useful when you have to set the entire attribute at once.
   • Cons:
     • Slow due to the overhead of manipulating attributes and can cause a reflow/repaint operation on the DOM.

6. classList (add)

   • Description: This method is used to manipulate the class list of an element, allowing you to add or remove classes.
   • Pros:
     • Fast and efficient; can easily toggle styles applied via CSS classes.
     • Keeps JavaScript and CSS concerns separated, improving maintainability.
   • Cons:
     • Requires the pre-definition of classes in CSS, which may not always be feasible if styles are dynamic.

Benchmark Results

From the benchmark results provided:

• Fastest Method: setAttribute executed at approximately 1036 executions per second.
• Moderately Fast Methods: classList (around 807 executions per second) and style.setProperty (around 408 executions per second).
• Slowest Methods: style.cssText (around 102 executions per second), style (around 92 executions per second), and Object.assign (around 89 executions per second).

Other Considerations

1. Performance Impact: The choice of styling method has a significant impact on performance, particularly in scenarios involving frequent updates (like animations or dynamic styling).

2. Maintainability: While performance is essential, maintaining readable and manageable code should also be a priority.

3. Browser Compatibility: Different browsers may optimize these operations differently, which might impact performance in real-world scenarios.

Alternatives

Other alternatives for styling could have included:

• CSS variables: When supported, CSS variables can be manipulated dynamically, optimizing for performance while providing flexibility.
• JavaScript frameworks: Libraries and frameworks like React or Vue have their methods for style manipulation that might abstract away some of these performance considerations but come with their overhead.

In conclusion, the choice of method for applying styles in JavaScript has significant implications for both performance and maintainability, and developers should choose based on the specific requirements of their applications while performing due diligence through testing.