Wrap mutant. React

Object mutation is easy and extremelly fast. But such libraries like react make us to rebuild objects on every their change. It's not a problem on simple and small objects. When your object is a big array, your application become slow. When you are trying to handle complicated deeply nested object, it becomes a brain cancer.

Solution is in wrapping that big or complex objects into Proxy object.

Examples

reactflow example [demo | repo]

• /src/pages/projects/projects.tsx
• /src/lib/statemgr.ts

pravosleva's substring-highlight-sample [demo | repo]

• /src/pages/uremont/reviews/kai3341-sample/Sample.tsx

---

This package contains react integration. To understand how actually it works please read the docs of @wrap-mutant/core API V2. Don't be afraid, it's small.

useWMState

Classical example. We have avoided rebuilding on each render potencially large array. State update complexity does not depends on array size and always happens by O(1)

import React, { useCallback, useEffect } from "react";
import { useWMState } from "@wrap-mutant/react";

const recordFactory = () => [] as string[];

export const Blackboard = () => {
  const [records, updateRecords] = useWMState(recordFactory, { bind: true });

  const writeRecord = useCallback(() => {
    records.push("I will not skateboard in the halls.");
    updateRecords();
  }, [records, updateRecords]);

  useEffect(() => {
    const interval = setInterval(writeRecord, 250);
    return () => clearInterval(interval); // eslint-disable-next-line
  }, []);

  const renderedRecords = records.map((item, index) => (
    <div className="line" key={index}>
      {item}
    </div>
  ));

  return <div className="board">{renderedRecords}</div>;
};

It's possible to avoid all loops in this component via pushing into records array rendered JSX.Element instead of string. But keep in mind it's dirty hack. Of course, we will talk about it next at createMutableContext and @wrap-mutant/react-rendered-array :)

API reference:

• Required factory function, passed directly useMemo
• Optional options: object:
  • deps: Optional dependency Array, passed directly useMemo. Default: []
  • bind: Optional boolean flag should we call utility bindCallables defined at @wrap-mutant/util. Default: false. Read more explaination in Pitfalls section
  • args: Optional any generic parameter passed into factory function (first parameter). Allows you to move complicated factory functions outside your FunctionalComponent closure to improve your code readability and performance
  • wrap: Optional boolean meaning should we wrap the target object or not. Default: true
  • count: Optional number parameter meaning how many wrapper objects will be pre-created. More info at @wrap-mutant/core API V2

---

createMutableContext

Now I imagine you say "WAAAT?", but I'll explain :). This is auxiliary tool created for @wrap-mutant/react-rendered-array-like objects. And if you think it's useless -- start from reading about @wrap-mutant/react-rendered-array, and then welcome here.

In very short words MutableContext is the way to keep actual callbacks without element re-rendering. This is the only way to pass new callbacks into @wrap-mutant/react-rendered-array array-like objects without their's re-render.

Be really careful in MutableContext usage. Be sure you understand how actually react works and why does render triggers.

Usage is absolutelly the same as regular context. Limitations:

• You have to pass Object-like value anyway even you have the only callback
• NEVER unpack this context. Read How do JavaScript closures work?

import { createMutableContext } from "@wrap-mutant/react";

const ReviewsItemCTX = createMutableContext({ updateItem: (diff: any) => {} });

const ItemRender = (props: Item) => {
  const ctx = useContext(ReviewsItemCTX); // <= DO NOT UNPACK
  return (
    <ReviewsItem item={props} updateItem={(diff) => ctx.updateItem(diff)} />
    // ALSO WRONG updateItem={ctx.updateItem}
  );
};

const Container = () => {
  // ... All code skipped. You  can see more at examples
  // prettier-ignore
  const updateItem = useCallback(
    (diff: any) => {/* do update state */},
    [/* requirements. Everything as usual */],
  );
  return (
    // Again. Context value have to be Object-like
    <ReviewsItemCTX.Provider value={{ updateItem }}>
      {/* children */}
    </ReviewsItemCTX.Provider>
  );
};

All these weird things are created to make possible implementation for @wrap-mutant/react-rendered-array-like objects

---

re-exports

from @wrap-mutant/core API V2:

import { wrap, toggle, HasWrapperGen } from "@wrap-mutant/react";

• function wrap is renamed export of @wrap-mutant/core's wrapCached
• function toggle is renamed export of @wrap-mutant/core's toggleCached
• type HasWrapperGen is @wrap-mutant/core's HasWrapperGen

from @wrap-mutant/utils:

import { bindCallables } from "@wrap-mutant/react";

• function bindCallables is @wrap-mutant/utils's bindCallables

---

Pitfalls

Wrapped target object's methods behavior changes by Proxy object -- they loose their's this. There is an example:

import { wrap } from "@wrap-mutant/react";

const A = wrap([] as number[]);
A.push(1, 2, 3, 4, 5); // <== throws an Error
A.forEach(concole.log); // <== throws an Error too

In this example push and forEach methods lost their's this. More commonly used map method also loose his this. Solution:

import { wrap, bindCallables } from "@wrap-mutant/react";

const A = wrap(bindCallables([] as number[]));
A.push(1, 2, 3, 4, 5); // <== OK
A.forEach(concole.log); // <== OK

It means before wrapping you have to apply bindCallables to target object. And exactly this is a meaning of bind option of useWMState hook.

General rule sounds like:

If you are calling methods of wrapped object and you are sure these methods implementation is not an arrow function, you have to bind callables before wrapping.

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Any questions?

Don't be afraid to open this library source code -- it's really small. Also we have Telegram Community