Add makeRange() helper method

index.d.ts

@@ -10,9 +10,21 @@ export interface Options {
 	readonly host?: string;
 }
 
-/**
- * Get an available TCP port number.
- *
- * @returns Port number.
- */
-export default function getPort(options?: Options): Promise<number>;
+declare const getPort: {
+  /**
+   * Get an available TCP port number.
+   *
+   * @returns Port number.
+   */
+  (options?: Options): Promise<number>;
+
+  /**
+   * Make a range of ports [from,to).
+   * @param from - First port of range(inclusive)
+   * @param to - Last port of range(exclusive)
+   * @returns Array with ports in range.
+   */
+  makeRange(from: number, to: number): number[];
+}
+
+export default getPort;

index.js

@@ -32,4 +32,29 @@ module.exports = options => options ?
 	getPort(options).catch(() => getPort(Object.assign(options, {port: 0}))) :
 	getPort({port: 0});
 
+module.exports.makeRange = (from, to) => {
+	if (!Number.isInteger(from) || !Number.isInteger(to)) {
+		throw new TypeError('`from` and `to` must ne integer numbers');
+	}
+
+	if (from < 1025 || from > 65535) {
+		throw new RangeError('`from` must be between 1025 and 65535');
+	}
+
+	if (to < 1025 || to > 65536) {
+		throw new RangeError('`to` must be between 1025 and 65536');
+	}
+
+	if (from >= to) {
+		throw new RangeError('`to` must be greater than `from`');
+	}
+
+	const ports = [];
+	for (let port = from; port < to; port++) {
+		ports.push(port);
+	}
+
+	return ports;
+};
+
 module.exports.default = module.exports;

index.test-d.ts

@@ -5,3 +5,5 @@ expectType<number>(await getPort());
 expectType<number>(await getPort({port: 3000}));
 expectType<number>(await getPort({port: [3000, 3001, 3002]}));
 expectType<number>(await getPort({host: 'https://localhost'}));
+
+expectType<number[]>(await getPort.makeRange(1025, 1026));

readme.md

@@ -39,6 +39,15 @@ Pass in an array of preferred ports:
 })();
 ```
 
+Use `makeRange` in case you need to select port from a range:
+
+```js
+(async () => {
+  console.log(await getPort({port: getPort.makeRange(3000, 3003)}));
+  // Will use any port >= 3000, port < 3003, otherwise fall back to a random port
+})();
+```
+
 ## API
 
 ### getPort([options])

test.js

@@ -93,3 +93,15 @@ test('all preferred ports in array are unavailable', async t => {
 	t.not(port, desiredPorts[0]);
 	t.not(port, desiredPorts[1]);
 });
+
+test('makeRange throws on invalid ranges', t => {
+	t.throws(() => getPort.makeRange(0, 0));
+	t.throws(() => getPort.makeRange(1024, 1024));
+	t.throws(() => getPort.makeRange(65536, 65536));
+	t.throws(() => getPort.makeRange(1026, 1025));
+});
+
+test('makeRange produces valid ranges', t => {
+	t.deepEqual(getPort.makeRange(1025, 1026), [1025]);
+	t.deepEqual(getPort.makeRange(1025, 1028), [1025, 1026, 1027]);
+});