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54 lines
1.9 KiB
TypeScript
54 lines
1.9 KiB
TypeScript
import React, { memo, useContext, useRef, useState } from 'react';
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import { fireEvent, getNodeText, render } from '../../../tests/utils';
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import Anchor from '../Anchor';
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import AnchorContext from '../context';
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// we use'memo' here in order to only render inner component while context changed.
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const CacheInner = memo(() => {
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const countRef = useRef(0);
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countRef.current++;
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// subscribe anchor context
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useContext(AnchorContext);
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return (
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<div>
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Child Rendering Count: <span id="child_count">{countRef.current}</span>
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</div>
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);
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});
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const CacheOuter = () => {
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// We use 'useState' here in order to trigger parent component rendering.
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const [count, setCount] = useState(1);
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const handleClick = () => {
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setCount(count + 1);
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};
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// During each rendering phase, the cached context value returned from method 'Anchor#getMemoizedContextValue' will take effect.
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// So 'CacheInner' component won't rerender.
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return (
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<div>
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<button type="button" onClick={handleClick} id="parent_btn">
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Click
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</button>
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Parent Rendering Count: <span id="parent_count">{count}</span>
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<Anchor affix={false}>
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<CacheInner />
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</Anchor>
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</div>
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);
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};
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it("Rendering on Anchor without changed AnchorContext won't trigger rendering on child component.", () => {
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const { container } = render(<CacheOuter />);
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const childCount = getNodeText(container.querySelector('#child_count')!);
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fireEvent.click(container.querySelector('#parent_btn')!);
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expect(getNodeText(container.querySelector('#parent_count')!)).toBe('2');
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// child component won't rerender
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expect(getNodeText(container.querySelector('#child_count')!)).toBe(childCount);
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fireEvent.click(container.querySelector('#parent_btn')!);
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expect(getNodeText(container.querySelector('#parent_count')!)).toBe('3');
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// child component won't rerender
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expect(getNodeText(container.querySelector('#child_count')!)).toBe(childCount);
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});
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