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Igor Sukharev
Igor Sukharev

Posted on • Updated on

Fusor vs React

Fusor is a simple JavaScript library that declaratively manages DOM

Common features

Fusor was inspired by React, and they both share the same ideas:

  • Composable functional components
  • One-way data flow
  • JSX
  • DOM updates only if a value or reference changes
  • Updates to the parent component will trigger the necessary updates in its children

The main difference

The fundamental difference lies in the separation of concerns within the component lifecycle (aka single-responsibility principle in SOLID)

Fusor React
Component creation create() create_update()
Component changing state = x setState(x) + create_update()
Component updating update() create_update()

Benefits

Fusor React
Component data Created once on initialization Created on initialization and recreated on every update
Side effects Normal JavaScript flow Complex and verbose hooks mechanics
Component updates Explicit, update what and when you need Implicit, complex
Component functions Pure Context is required
Library size (gz) ~2kB ~44kB

Code samples

Fusor React Comment
Create state let x = 0 const [x, setX] = useState(0)
Update state x = 1 setX(1)
Update DOM update() setX(1) both are manual calls
Static prop/child <p id={x}>{y}</p> <p id={x}>{y}</p> exactly the same
Dynamic prop/child <p id={() => x}>{() => y}</p> <p id={x}>{y}</p> callbacks used for dynamic values

Application example

Fusor-vs-React-counting-button-application

The click$e$update means:

  • click
  • event handler
  • update DOM when handler completes
  • $ separator symbol
  • full reference

However

Fusor avoids recreating component data with every update,
preventing a change in the click event handler function reference. This can be important for performance. As a result, useCallback should be employed in React example to achieve feature parity.

const CountingButton = () => {
  const [count, setCount] = useState(0);
  const handleClick = useCallback(() => setCount((count) => count + 1), []);
  return <button onClick={handleClick}>Clicked {count} times</button>;
};
Enter fullscreen mode Exit fullscreen mode

Verbosity analysis

Verbosity - number of symbols without whitespace

Component Fusor React
CountingButton 116 189
AnalogClock 776 783
RequestUsers 1072 1181

Source code

Other differences

Fusor React
DOM Real Virtual
Events Native Synthetic
Lifecycle Native Complex mechanics
Attribute names W3C Specification Mangled
Web components support Complete Incomplete

Why Fusor

  • It is simple, lightweight, explicit, flexible and compatible
  • It extensively utilizes modern JavaScript and browser features
  • It follows the principle of doing one thing and doing it well (managing DOM elements)
  • It has zero dependencies and is only around 2kB in size

PS

Fusor repo: https://github.com/fusorjs/dom

Thank you!

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