1 files changed, 158 insertions, 0 deletions
diff --git a/preact/src/diff/props.js b/preact/src/diff/props.js
new file mode 100644
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--- /dev/null
+++ b/preact/src/diff/props.js
@@ -0,0 +1,158 @@
+import { IS_NON_DIMENSIONAL } from '../constants';
+import options from '../options';
+
+/**
+ * Diff the old and new properties of a VNode and apply changes to the DOM node
+ * @param {import('../internal').PreactElement} dom The DOM node to apply
+ * changes to
+ * @param {object} newProps The new props
+ * @param {object} oldProps The old props
+ * @param {boolean} isSvg Whether or not this node is an SVG node
+ * @param {boolean} hydrate Whether or not we are in hydration mode
+ */
+export function diffProps(dom, newProps, oldProps, isSvg, hydrate) {
+	let i;
+
+	for (i in oldProps) {
+		if (i !== 'children' && i !== 'key' && !(i in newProps)) {
+			setProperty(dom, i, null, oldProps[i], isSvg);
+		}
+	}
+
+	for (i in newProps) {
+		if (
+			(!hydrate || typeof newProps[i] == 'function') &&
+			i !== 'children' &&
+			i !== 'key' &&
+			i !== 'value' &&
+			i !== 'checked' &&
+			oldProps[i] !== newProps[i]
+		) {
+			setProperty(dom, i, newProps[i], oldProps[i], isSvg);
+		}
+	}
+}
+
+function setStyle(style, key, value) {
+	if (key[0] === '-') {
+		style.setProperty(key, value);
+	} else if (value == null) {
+		style[key] = '';
+	} else if (typeof value != 'number' || IS_NON_DIMENSIONAL.test(key)) {
+		style[key] = value;
+	} else {
+		style[key] = value + 'px';
+	}
+}
+
+/**
+ * Set a property value on a DOM node
+ * @param {import('../internal').PreactElement} dom The DOM node to modify
+ * @param {string} name The name of the property to set
+ * @param {*} value The value to set the property to
+ * @param {*} oldValue The old value the property had
+ * @param {boolean} isSvg Whether or not this DOM node is an SVG node or not
+ */
+export function setProperty(dom, name, value, oldValue, isSvg) {
+	let useCapture;
+
+	o: if (name === 'style') {
+		if (typeof value == 'string') {
+			dom.style.cssText = value;
+		} else {
+			if (typeof oldValue == 'string') {
+				dom.style.cssText = oldValue = '';
+			}
+
+			if (oldValue) {
+				for (name in oldValue) {
+					if (!(value && name in value)) {
+						setStyle(dom.style, name, '');
+					}
+				}
+			}
+
+			if (value) {
+				for (name in value) {
+					if (!oldValue || value[name] !== oldValue[name]) {
+						setStyle(dom.style, name, value[name]);
+					}
+				}
+			}
+		}
+	}
+	// Benchmark for comparison: https://esbench.com/bench/574c954bdb965b9a00965ac6
+	else if (name[0] === 'o' && name[1] === 'n') {
+		useCapture = name !== (name = name.replace(/Capture$/, ''));
+
+		// Infer correct casing for DOM built-in events:
+		if (name.toLowerCase() in dom) name = name.toLowerCase().slice(2);
+		else name = name.slice(2);
+
+		if (!dom._listeners) dom._listeners = {};
+		dom._listeners[name + useCapture] = value;
+
+		if (value) {
+			if (!oldValue) {
+				const handler = useCapture ? eventProxyCapture : eventProxy;
+				dom.addEventListener(name, handler, useCapture);
+			}
+		} else {
+			const handler = useCapture ? eventProxyCapture : eventProxy;
+			dom.removeEventListener(name, handler, useCapture);
+		}
+	} else if (name !== 'dangerouslySetInnerHTML') {
+		if (isSvg) {
+			// Normalize incorrect prop usage for SVG:
+			// - xlink:href / xlinkHref --> href (xlink:href was removed from SVG and isn't needed)
+			// - className --> class
+			name = name.replace(/xlink[H:h]/, 'h').replace(/sName$/, 's');
+		} else if (
+			name !== 'href' &&
+			name !== 'list' &&
+			name !== 'form' &&
+			// Default value in browsers is `-1` and an empty string is
+			// cast to `0` instead
+			name !== 'tabIndex' &&
+			name !== 'download' &&
+			name in dom
+		) {
+			try {
+				dom[name] = value == null ? '' : value;
+				// labelled break is 1b smaller here than a return statement (sorry)
+				break o;
+			} catch (e) {}
+		}
+
+		// ARIA-attributes have a different notion of boolean values.
+		// The value `false` is different from the attribute not
+		// existing on the DOM, so we can't remove it. For non-boolean
+		// ARIA-attributes we could treat false as a removal, but the
+		// amount of exceptions would cost us too many bytes. On top of
+		// that other VDOM frameworks also always stringify `false`.
+
+		if (typeof value === 'function') {
+			// never serialize functions as attribute values
+		} else if (
+			value != null &&
+			(value !== false || (name[0] === 'a' && name[1] === 'r'))
+		) {
+			dom.setAttribute(name, value);
+		} else {
+			dom.removeAttribute(name);
+		}
+	}
+}
+
+/**
+ * Proxy an event to hooked event handlers
+ * @param {Event} e The event object from the browser
+ * @private
+ */
+function eventProxy(e) {
+	this._listeners[e.type + false](options.event ? options.event(e) : e);
+}
+
+function eventProxyCapture(e) {
+	this._listeners[e.type + true](options.event ? options.event(e) : e);
+}