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