Completed exercise 4.4

Author: 0mppula

5_higher-order_functions/dominant_writing_function.js

@@ -0,0 +1,47 @@
+// load dependencies
+require('./scripts.js');
+
+const countBy = (items, groupName) => {
+	let counts = [];
+
+	for (let item of items) {
+		let name = groupName(item);
+		let known = counts.findIndex((count) => count.name === name);
+		if (known === -1) {
+			counts.push({ name, count: 1 });
+		} else {
+			counts[known].count++;
+		}
+	}
+
+	return counts;
+};
+
+const characterScript = (code) => {
+	for (let script of SCRIPTS) {
+		if (
+			script.ranges.some(([from, to]) => {
+				return code >= from && code < to;
+			})
+		) {
+			return script;
+		}
+	}
+	return null;
+};
+
+const dominantDirection = (text) => {
+	const directions = countBy(text, (char) => {
+		let script = characterScript(char.codePointAt(0));
+		return script ? script.direction : 'none';
+	}).filter(({ name }) => name !== 'none');
+
+	if (directions.length === 0) return 'none';
+
+	return directions.reduce((a, b) => (a.count > b.count ? a : b)).name;
+};
+
+console.log(dominantDirection('Hello!'));
+// → ltr
+console.log(dominantDirection('Hey, مساء الخير'));
+// → rtl