Respect timezones when converting dates

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@ztimson/utils",
-	"version": "0.27.1",
+	"version": "0.27.4",
 	"description": "Utility library",
 	"author": "Zak Timson",
 	"license": "MIT",

src/objects.ts

@@ -1,22 +1,28 @@
 export type Delta = { [key: string]: any | Delta | null };
 
+
 /**
- * Applies deltas in order to modify `target`.
- * @param base - Original
- * @param deltas - List of deltas to apply
+ * Applies deltas to `target`.
+ * @param base starting point
+ * @param deltas List of deltas to apply
  * @returns Mutated target
  */
-export function applyDelta(base: any, deltas: any): any {
-	if(deltas === null) return null;
-	if(typeof base !== 'object' || base === null) return deltas === undefined ? base : deltas;
-	const result = Array.isArray(base) ? [...base] : { ...base };
-	for(const key in deltas) {
-		const val = deltas[key];
-		if (val === undefined) delete result[key];
-		else if (typeof val === 'object' && val !== null && !(Array.isArray(val))) result[key] = applyDelta(result[key], val);
-		else result[key] = val;
+export function applyDeltas(base: any, ...deltas: any[]): any {
+	function applyDelta(base: any, delta: any): any {
+		if(delta === null) return null;
+		if(typeof base !== 'object' || base === null) return delta === undefined ? base : delta;
+		const result = Array.isArray(base) ? [...base] : { ...base };
+		for(const key in delta) {
+			const val = delta[key];
+			if(val === undefined) delete result[key];
+			else if(typeof val === 'object' && val !== null && !Array.isArray(val)) result[key] = applyDelta(result[key], val);
+			else result[key] = val;
+		}
+		return result;
 	}
-	return result;
+
+	for(const d of deltas.flat()) base = applyDelta(base, d?.delta ?? d);
+	return base;
 }
 
 /**
@@ -34,7 +40,7 @@ export function calcDelta(old: any, updated: any): any {
 		const newVal = updated?.[key];
 		if(isObj(oldVal) && isObj(newVal)) {
 			const nested = calcDelta(oldVal, newVal);
-			if (nested !== null && Object.keys(nested).length > 0) delta[key] = nested;
+			if(nested !== null && Object.keys(nested).length > 0) delta[key] = nested;
 		} else if(JSON.stringify(oldVal) !== JSON.stringify(newVal)) {
 			delta[key] = newVal;
 		}
@@ -319,8 +325,8 @@ export function JSONSerialize<T1>(obj: T1): T1 | string {
 export function JSONSanitize(obj: any, space?: number): string {
 	const cache: any[] = [];
 	return JSON.stringify(obj, (key, value) => {
-		if (typeof value === 'object' && value !== null) {
-			if (cache.includes(value)) return '[Circular]';
+		if(typeof value === 'object' && value !== null) {
+			if(cache.includes(value)) return '[Circular]';
 			cache.push(value);
 		}
 		return value;

src/time.ts

@@ -55,23 +55,46 @@ export function formatDate(format: string = 'YYYY-MM-DD H:mm', date: Date | numb
 	}
 
 	let zonedDate = new Date(date);
+	let get: (fn: 'FullYear' | 'Month' | 'Date' | 'Day' | 'Hours' | 'Minutes' | 'Seconds' | 'Milliseconds') => number;
+	const partsMap: Record<string, string> = {};
 	if (!numericTz && tzName !== 'UTC') {
 		const parts = new Intl.DateTimeFormat('en-US', {
 			timeZone: tzName,
-			year: 'numeric', month: '2-digit', day: '2-digit',
+			year: 'numeric', month: '2-digit', day: '2-digit', weekday: 'long',
 			hour: '2-digit', minute: '2-digit', second: '2-digit',
 			hour12: false
 		}).formatToParts(date);
-		const get = (type: string) => parts.find(p => p.type === type)?.value;
-		const build = `${get('year')}-${get('month')}-${get('day')}T${get('hour')}:${get('minute')}:${get('second')}Z`;
-		zonedDate = new Date(build);
-	} else if (numericTz || tzName === 'UTC') {
+		parts.forEach(p => {
+			partsMap[p.type] = p.value;
+		});
+
+		const monthValue = parseInt(partsMap.month) - 1;
+		const dayOfWeekValue = new Date(`${partsMap.year}-${partsMap.month}-${partsMap.day}`).getDay();
+		const hourValue = parseInt(partsMap.hour);
+
+		get = (fn: 'FullYear' | 'Month' | 'Date' | 'Day' | 'Hours' | 'Minutes' | 'Seconds' | 'Milliseconds'): number => {
+			switch (fn) {
+				case 'FullYear': return parseInt(partsMap.year);
+				case 'Month': return monthValue;
+				case 'Date': return parseInt(partsMap.day);
+				case 'Day': return dayOfWeekValue;
+				case 'Hours': return hourValue;
+				case 'Minutes': return parseInt(partsMap.minute);
+				case 'Seconds': return parseInt(partsMap.second);
+				default: return 0;
+			}
+		};
+	} else {
 		const offset = numericTz ? tz as number : 0;
 		zonedDate = new Date(date.getTime() + offset * 60 * 60 * 1000);
+		get = (fn: 'FullYear' | 'Month' | 'Date' | 'Day' | 'Hours' | 'Minutes' | 'Seconds' | 'Milliseconds'): number => zonedDate[`getUTC${fn}`]();
 	}
 
-	const get = (fn: 'FullYear' | 'Month' | 'Date' | 'Day' | 'Hours' | 'Minutes' | 'Seconds' | 'Milliseconds') =>
-		(numericTz || tzName === 'UTC') ? zonedDate[`getUTC${fn}`]() : zonedDate[`get${fn}`]();
+	function numSuffix(n: number): string {
+		const s = ["th", "st", "nd", "rd"];
+		const v = n % 100;
+		return n + (s[(v - 20) % 10] || s[v] || s[0]);
+	}
 
 	function getTZOffset(): string {
 		if (numericTz) {
@@ -119,7 +142,7 @@ export function formatDate(format: string = 'YYYY-MM-DD H:mm', date: Date | numb
 		m: get('Minutes').toString(),
 		ss: get('Seconds').toString().padStart(2, '0'),
 		s: get('Seconds').toString(),
-		SSS: get('Milliseconds').toString().padStart(3, '0'),
+		SSS: (zonedDate[`getUTC${'Milliseconds'}`]()).toString().padStart(3, '0'),
 		A: get('Hours') >= 12 ? 'PM' : 'AM',
 		a: get('Hours') >= 12 ? 'pm' : 'am',
 		ZZ: getTZOffset().replace(':', ''),