160 lines
4.6 KiB
TypeScript
160 lines
4.6 KiB
TypeScript
import MutationQueue from "./MutationQueue"
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// Diff provides diffing utilities to morph existing DOM elements
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// into the target HTML string.
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//
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// Example:
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// Diff.innerHTML(body, "<div>This is my new content</div>")
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//
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// Whatever contents will be in the body, they will be re-used and morphed
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// into the new DOM defined by a simple HTML string. This is useful for
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// Single Page Applications that use server rendered content. The server
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// responds with the pre-rendered HTML and we can simply morph our current
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// contents into the next page.
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export default class Diff {
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static persistentClasses = new Set<string>()
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static persistentAttributes = new Set<string>()
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static mutations: MutationQueue = new MutationQueue()
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// innerHTML will diff the element with the given HTML string and apply DOM mutations.
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static innerHTML(aRoot: HTMLElement, html: string): Promise<void> {
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const container = document.createElement("main")
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container.innerHTML = html
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return new Promise((resolve, _) => {
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Diff.childNodes(aRoot, container)
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this.mutations.wait(resolve)
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})
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}
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// root will diff the document root element with the given HTML string and apply DOM mutations.
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static root(aRoot: HTMLElement, html: string) {
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return new Promise((resolve, _) => {
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const rootContainer = document.createElement("html")
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rootContainer.innerHTML = html.replace("<!DOCTYPE html>", "")
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Diff.childNodes(aRoot.getElementsByTagName("body")[0], rootContainer.getElementsByTagName("body")[0])
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this.mutations.wait(resolve)
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})
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}
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// childNodes diffs the child nodes of 2 given elements and applies DOM mutations.
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static childNodes(aRoot: Node, bRoot: Node) {
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const aChild = [...aRoot.childNodes]
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const bChild = [...bRoot.childNodes]
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const numNodes = Math.max(aChild.length, bChild.length)
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for(let i = 0; i < numNodes; i++) {
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const a = aChild[i]
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// Remove nodes at the end of a that do not exist in b
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if(i >= bChild.length) {
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this.mutations.queue(() => aRoot.removeChild(a))
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continue
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}
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const b = bChild[i]
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// If a doesn't have that many nodes, simply append at the end of a
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if(i >= aChild.length) {
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this.mutations.queue(() => aRoot.appendChild(b))
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continue
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}
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// If it's a completely different HTML tag or node type, replace it
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if(a.nodeName !== b.nodeName || a.nodeType !== b.nodeType) {
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this.mutations.queue(() => aRoot.replaceChild(b, a))
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continue
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}
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// Text node:
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// We don't need to check for b to be a text node as well because
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// we eliminated different node types in the previous condition.
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if(a.nodeType === Node.TEXT_NODE) {
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this.mutations.queue(() => a.textContent = b.textContent)
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continue
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}
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// HTML element:
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if(a.nodeType === Node.ELEMENT_NODE) {
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const elemA = a as HTMLElement
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const elemB = b as HTMLElement
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const removeAttributes: Attr[] = []
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for(let x = 0; x < elemA.attributes.length; x++) {
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const attrib = elemA.attributes[x]
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if(attrib.specified) {
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if(!elemB.hasAttribute(attrib.name) && !Diff.persistentAttributes.has(attrib.name)) {
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removeAttributes.push(attrib)
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}
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}
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}
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this.mutations.queue(() => {
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for(const attr of removeAttributes) {
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elemA.removeAttributeNode(attr)
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}
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})
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for(let x = 0; x < elemB.attributes.length; x++) {
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const attrib = elemB.attributes[x]
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if(!attrib.specified) {
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continue
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}
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// If the attribute value is exactly the same, skip this attribute.
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if(elemA.getAttribute(attrib.name) === attrib.value) {
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continue
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}
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if(attrib.name === "class") {
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const classesA = elemA.classList
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const classesB = elemB.classList
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const removeClasses: string[] = []
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for(const className of classesA) {
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if(!classesB.contains(className) && !Diff.persistentClasses.has(className)) {
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removeClasses.push(className)
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}
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}
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this.mutations.queue(() => {
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for(const className of removeClasses) {
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classesA.remove(className)
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}
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for(const className of classesB) {
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if(!classesA.contains(className)) {
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classesA.add(className)
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}
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}
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})
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continue
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}
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this.mutations.queue(() => elemA.setAttribute(attrib.name, attrib.value))
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}
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// Special case: Apply state of input elements
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if(elemA !== document.activeElement && elemA instanceof HTMLInputElement && elemB instanceof HTMLInputElement) {
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this.mutations.queue(() => {
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(elemA as HTMLInputElement).value = (elemB as HTMLInputElement).value
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})
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}
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}
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// Never diff the contents of web components
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if(a.nodeName.includes("-")) {
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continue
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}
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// Child nodes
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Diff.childNodes(a, b)
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}
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}
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}
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