Prefer TypeScript inference over explicit types

- Remove explicit return types from functions where inference works
- Use as const for tuple inference in getMinMax
- Remove return type annotations from destructuring examples

Author: kentcdodds

exercises/03.tuples/01.solution.fixed-length/index.ts

@@ -5,14 +5,14 @@ const nyc: [number, number] = [40.7128, -74.006]
 
 const la: [number, number] = [34.0522, -118.2437]
 
-function formatCoordinate([lat, long]: [number, number]): string {
+function formatCoordinate([lat, long]: [number, number]) {
 	return `Lat: ${lat}, Long: ${long}`
 }
 
 function getDistance(
 	[lat1, long1]: [number, number],
 	[lat2, long2]: [number, number],
-): number {
+) {
 	const latDiff = lat2 - lat1
 	const longDiff = long2 - long1
 	return Math.sqrt(Math.pow(latDiff, 2) + Math.pow(longDiff, 2))

exercises/05.enums/01.solution.string-enums/index.ts

@@ -14,7 +14,7 @@ const order = {
 	customerName: 'Alice Johnson',
 }
 
-function getStatusMessage(status: OrderStatus): string {
+function getStatusMessage(status: OrderStatus) {
 	switch (status) {
 		case OrderStatus.Pending:
 			return 'Your order is pending confirmation'

exercises/06.destructuring/01.solution.object-destructuring/index.ts

@@ -26,7 +26,7 @@ const { id: userId } = user
 const { bio = 'No bio provided' } = user
 
 // Function with parameter destructuring
-function formatUserCard({ name, email, role }: User): string {
+function formatUserCard({ name, email, role }: User) {
 	return `${name} (${role}) - ${email}`
 }
 

exercises/06.destructuring/02.solution.array-destructuring/index.ts

@@ -15,9 +15,9 @@ const coordinates: [number, number, number] = [10, 20, 30]
 const [x, y, z] = coordinates
 
 // Function returning tuple, then destructuring result
-function getMinMax(nums: Array<number>): [number, number] {
+function getMinMax(nums: Array<number>) {
 	const sorted = [...nums].sort((a, b) => a - b)
-	return [sorted[0], sorted[sorted.length - 1]]
+	return [sorted[0], sorted[sorted.length - 1]] as const
 }
 
 const [min, max] = getMinMax(scores)

exercises/07.spread-rest/02.solution.rest-parameters/index.ts

@@ -2,25 +2,25 @@
 // Functions that accept variable numbers of arguments
 
 // Rest parameters collect all arguments into an array
-function multiply(...numbers: Array<number>): number {
+function multiply(...numbers: Array<number>) {
 	if (numbers.length === 0) return 1
 	return numbers.reduce((a, b) => a * b, 1)
 }
 
 // Combining regular parameter with rest
-function logWithPrefix(prefix: string, ...messages: Array<string>): void {
+function logWithPrefix(prefix: string, ...messages: Array<string>) {
 	for (const message of messages) {
 		console.log(`${prefix} ${message}`)
 	}
 }
 
 // Generic rest parameters
-function createArray<T>(...items: Array<T>): Array<T> {
+function createArray<T>(...items: Array<T>) {
 	return items
 }
 
 // Rest + spread combo - collect arrays, spread to merge
-function mergeArrays<T>(...arrays: Array<Array<T>>): Array<T> {
+function mergeArrays<T>(...arrays: Array<Array<T>>) {
 	const result: Array<T> = []
 	for (const arr of arrays) {
 		result.push(...arr)