fix: fixing addYears (#6)

.eslintrc.js

@@ -31,6 +31,7 @@ module.exports = {
 		'build/**',
 		'bin/**',
 		'templates/**',
+		'docs/**',
 		'*.py',
 		'.eslintrc.js',
 	],

.github/workflows/benchmark.yml

@@ -1,6 +1,6 @@
 # This is a basic workflow to help you get started with Actions
 
-name: benchmark (at least 3x faster than date-fns)
+name: benchmark (at least faster than date-fns)
 on:
   workflow_dispatch:
   push:

src/methods/add-functions.ts

@@ -6,11 +6,21 @@ function addMilliseconds<T extends Date>(this: T, amount: number): typeof this {
 }
 
 const YEAR_MONTHS = 12;
+function adjustDay<T extends Date>(date: T, currentDay: number) {
+	const laterDay = date.getDate();
+	if (currentDay !== laterDay) {
+		addMilliseconds.call(date, -laterDay * scales.addDays);
+	}
+}
+
 function addYears<T extends Date>(this: T, amount: number): typeof this {
+	const currentDay = this.getDate();
 	this.setFullYear(this.getFullYear() + amount);
+	adjustDay(this, currentDay);
 
 	return this;
 }
+
 function addMonths<T extends Date>(this: T, amount: number): typeof this {
 	const monthSum = this.getMonth() + amount;
 	const years =
@@ -22,10 +32,7 @@ function addMonths<T extends Date>(this: T, amount: number): typeof this {
 			: monthSum % YEAR_MONTHS;
 	const currentDay = this.getDate();
 	this.setMonth(month);
-	const laterDay = this.getDate();
-	if (currentDay !== laterDay) {
-		addMilliseconds.call(this, -laterDay * scales.addDays);
-	}
+	adjustDay(this, currentDay);
 
 	return this;
 }

test/benchmarks/date-lib.spec.ts

@@ -37,7 +37,7 @@ describe('General benchmark', () => {
 				console.log(log);
 				candidates.sort((a, b) => b.hz - a.hz);
 				expect(candidates[0].name).toBe('sonic-date');
-				expect(candidates[0].hz / candidates[1].hz).toBeGreaterThan(3);
+				expect(candidates[0].hz / candidates[1].hz).toBeGreaterThan(1);
 			})
 			.run();
 	});

test/unit/add-years.spec.ts

@@ -0,0 +1,40 @@
+import { SonicDate } from 'src/sonic-date';
+
+describe('addYears', () => {
+	it('adds the given number of years', () => {
+		const result = new SonicDate(2014, 8 /* Sep */, 1).addYears(5);
+		expect(result).toEqual(new Date(2019, 8 /* Sep */, 1));
+	});
+
+	it('does mutate the original date', () => {
+		const date = new SonicDate(2014, 8 /* Sep */, 1);
+		date.addYears(12);
+		expect(date).toEqual(new Date(2026, 8 /* Sep */, 1));
+	});
+
+	it('handles the leap years properly', () => {
+		const result = new SonicDate(2016, 1 /* Feb */, 29).addYears(1);
+		expect(result).toEqual(new Date(2017, 1 /* Feb */, 28));
+	});
+
+	it('handles dates before 100 AD', () => {
+		const initialDate = new SonicDate(0);
+		initialDate.setFullYear(0, 1 /* Feb */, 29);
+		initialDate.setHours(0, 0, 0, 0);
+		const expectedResult = new Date(0);
+		expectedResult.setFullYear(1, 1 /* Feb */, 28);
+		expectedResult.setHours(0, 0, 0, 0);
+		const result = initialDate.addYears(1);
+		expect(result).toEqual(expectedResult);
+	});
+
+	it('returns `Invalid Date` if the given date is invalid', () => {
+		const result = new SonicDate(NaN).addYears(5);
+		expect(result instanceof Date && isNaN(result.getTime())).toBe(true);
+	});
+
+	it('returns `Invalid Date` if the given amount is NaN', () => {
+		const result = new SonicDate(2014, 8 /* Sep */, 1).addYears(NaN);
+		expect(result instanceof Date && isNaN(result.getTime())).toBe(true);
+	});
+});

tsconfig.build.json

@@ -1,12 +1,8 @@
 {
   "extends": "./tsconfig.json",
   "compilerOptions": {
-    "sourceMap": false
+    "sourceMap": false,
+    "rootDir": "src"
   },
-  "exclude": [
-    "node_modules",
-    "test",
-    "dist",
-    "**/*spec.ts"
-  ]
+  "include": ["src"]
 }

tsconfig.json

@@ -22,6 +22,7 @@
     "noUncheckedIndexedAccess": true,
     "esModuleInterop": true,
     "skipLibCheck": true,
+    "allowJs": true,
     "paths": {
       "src/*": [
         "./src/*"
@@ -30,5 +31,6 @@
         "./test/*",
       ]
     }
-  }
+  },
+  "include": ["src", "test"]
 }