Add timeout option (#4)

Co-authored-by: Luke Batchelor <[email protected]>

.travis.yml

@@ -1,4 +1,4 @@
 language: node_js
 node_js:
+  - '8'
   - '6'
-  - '4'

index.js

@@ -1,20 +1,34 @@
 'use strict';
-module.exports = (condition, interval) => new Promise((resolve, reject) => {
-	interval = typeof interval === 'number' ? interval : 20;
+const pTimeout = require('p-timeout');
 
-	const check = () => {
-		Promise.resolve().then(condition).then(val => {
-			if (typeof val !== 'boolean') {
-				throw new TypeError('Expected condition to return a boolean');
-			}
+module.exports = (condition, opts) => {
+	opts = Object.assign({
+		interval: 20,
+		timeout: Infinity
+	}, opts);
+	const promise = new Promise((resolve, reject) => {
+		const check = () => {
+			Promise.resolve().then(condition).then(val => {
+				if (typeof val !== 'boolean') {
+					throw new TypeError('Expected condition to return a boolean');
+				}
 
-			if (val === true) {
-				resolve();
-			} else {
-				setTimeout(check, interval);
-			}
-		}).catch(reject);
-	};
+				if (val === true) {
+					resolve();
+				} else {
+					setTimeout(check, opts.interval);
+				}
+			}).catch(err => {
+				reject(err);
+			});
+		};
 
-	check();
-});
+		check();
+	});
+
+	if (opts.timeout !== Infinity) {
+		return pTimeout(promise, opts.timeout);
+	}
+
+	return promise;
+};

package.json

@@ -40,5 +40,8 @@
   },
   "xo": {
     "esnext": true
+  },
+  "dependencies": {
+    "p-timeout": "^2.0.1"
   }
 }

readme.md

@@ -26,7 +26,7 @@ pWaitFor(() => pathExists('unicorn.png')).then(() => {
 
 ## API
 
-### pWaitFor(condition, [interval])
+### pWaitFor(condition, [options])
 
 Returns a `Promise` that resolves when `condition` returns `true`. Rejects if `condition` throws or returns a `Promise` that rejects.
 
@@ -36,12 +36,21 @@ Type: `Function`
 
 Expected to return a `boolean` or a `Promise` for a `boolean`.
 
-#### interval
+#### options
+
+##### interval
 
 Type: `number`<br>
 Default: `20`
 
-Number of milliseconds to wait before retrying `condition`.
+Number of milliseconds to wait before retrying `condition`.  You can also pass a number in place of the options object to set the interval.
+
+##### timeout
+
+Type: `number`<br>
+Default: `Infinity`
+
+Number of milliseconds to wait before automatically rejecting.
 
 
 ## Related

test.js

@@ -1,7 +1,7 @@
 import test from 'ava';
 import delay from 'delay';
 import timeSpan from 'time-span';
-import m from './';
+import m from '.';
 
 const fixture = Symbol('unicorn');
 
@@ -16,3 +16,13 @@ test('waits for condition', async t => {
 test('rejects promise if condition rejects or throws', async t => {
 	await t.throws(m(() => Promise.reject(new Error('foo'))));
 });
+
+test('Will wait not longer than `timeout`ms before rejecting', async t => {
+	const end = timeSpan();
+	const ms = 200;
+	const maxWait = 100;
+	await t.throws(m(() => delay(ms).then(() => true), {interval: 20, timeout: maxWait}));
+	const timeTaken = end();
+	t.true(timeTaken < ms);
+	t.true(timeTaken > (maxWait - 20));
+});