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Check slice oldChildren perf #4596

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Check slice oldChildren perf #4596

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7259ee4
Check slice oldChildren perf
developit Dec 6, 2024
2f12e0a
Refactor children array construction logic
developit Dec 6, 2024
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19 changes: 12 additions & 7 deletions src/diff/children.js
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Original file line number Diff line number Diff line change
Expand Up @@ -69,15 +69,19 @@ export function diffChildren(

let newChildrenLength = renderResult.length;

let newChildren = new Array(newChildrenLength);
newParentVNode._children = newChildren;

oldDom = constructNewChildrenArray(
newParentVNode,
newChildren,
renderResult,
oldChildren,
oldDom
);

for (i = 0; i < newChildrenLength; i++) {
childVNode = newParentVNode._children[i];
childVNode = newChildren[i];
if (childVNode == null) continue;

// At this point, constructNewChildrenArray has assigned _index to be the
Expand Down Expand Up @@ -144,11 +148,13 @@ export function diffChildren(

/**
* @param {VNode} newParentVNode
* @param {VNode[]} newChildren
* @param {ComponentChildren[]} renderResult
* @param {VNode[]} oldChildren
*/
function constructNewChildrenArray(
newParentVNode,
newChildren,
renderResult,
oldChildren,
oldDom
Expand All @@ -166,7 +172,6 @@ function constructNewChildrenArray(

let skew = 0;

newParentVNode._children = new Array(newChildrenLength);
for (i = 0; i < newChildrenLength; i++) {
// @ts-expect-error We are reusing the childVNode variable to hold both the
// pre and post normalized childVNode
Expand All @@ -177,7 +182,7 @@ function constructNewChildrenArray(
typeof childVNode == 'boolean' ||
typeof childVNode == 'function'
) {
childVNode = newParentVNode._children[i] = null;
newChildren[i] = null;
continue;
}
// If this newVNode is being reused (e.g. <div>{reuse}{reuse}</div>) in the same diff,
Expand All @@ -190,15 +195,15 @@ function constructNewChildrenArray(
typeof childVNode == 'bigint' ||
childVNode.constructor == String
) {
childVNode = newParentVNode._children[i] = createVNode(
childVNode = newChildren[i] = createVNode(
null,
childVNode,
null,
null,
null
);
} else if (isArray(childVNode)) {
childVNode = newParentVNode._children[i] = createVNode(
childVNode = newChildren[i] = createVNode(
Fragment,
{ children: childVNode },
null,
Expand All @@ -210,15 +215,15 @@ function constructNewChildrenArray(
// scenario:
// const reuse = <div />
// <div>{reuse}<span />{reuse}</div>
childVNode = newParentVNode._children[i] = createVNode(
childVNode = newChildren[i] = createVNode(
childVNode.type,
childVNode.props,
childVNode.key,
childVNode.ref ? childVNode.ref : null,
childVNode._original
);
} else {
childVNode = newParentVNode._children[i] = childVNode;
childVNode = newChildren[i] = childVNode;
}

const skewedIndex = i + skew;
Expand Down
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