Restructure folders and add day 3's solution

javascript/day_02/part1.mjs

@@ -0,0 +1,36 @@
+import { readFile } from "fs/promises";
+
+function legalValues(a, b, gap) {
+	const delta = Math.abs(a - b);
+	console.log(`legaValues(${a}, ${b}, ${gap}){delta=${delta}} = ${delta <= gap}`);
+	return delta <= gap;
+};
+
+if (process.argv.length <= 2) {
+	console.error(`Needs more args >:(`).
+	process.exit(1);
+}
+
+const fileToRead = process.argv[2];
+const file = await readFile(fileToRead, `utf-8`);
+
+let validLines = 0;
+for (const line of file.split(`\n`)) {
+	// console.log(line)
+	const ints = line.split(` `)
+		.map(v => Number.parseInt(v));
+
+	const isSafe = ints
+		.slice(0, -1)
+		.map((v, i) => v - ints[i + 1])
+		.every((v, _, a) => Math.sign(v) === Math.sign(a[0]) && Math.abs(v) <= 3);
+
+	// console.log(isSafe)
+
+	if(isSafe) {
+		validLines++;
+	};
+	// break
+};
+
+console.log(`Number of valid reports:`, validLines)