diff --git a/docs/api.md b/docs/api.md
index 1b2f151f..3b88648b 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -296,7 +296,7 @@ The Puppeteer API is hierarchical and mirrors the browser structure.
 - [`BrowserContext`](#class-browsercontext) instance defines a browsing session and can own multiple pages.
 - [`Page`](#class-page) has at least one frame: main frame. There might be other frames created by [iframe](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe) or [frame](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/frame) tags.
 - [`Frame`](#class-frame) has at least one execution context - the default execution context - where the frame's JavaScript is executed. A Frame might have additional execution contexts that are associated with [extensions](https://developer.chrome.com/extensions).
-- [`Worker`](#class-worker) has a single execution context and and facilitates interacting with [WebWorkers](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API).
+- [`Worker`](#class-worker) has a single execution context and facilitates interacting with [WebWorkers](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API).
 
 (Diagram source: [link](https://docs.google.com/drawings/d/1Q_AM6KYs9kbyLZF-Lpp5mtpAWth73Cq8IKCsWYgi8MM/edit?usp=sharing))
 
@@ -1557,6 +1557,22 @@ This method behaves differently with respect to the type of the first parameter:
 - if `selectorOrFunctionOrTimeout` is a `number`, then the first argument is treated as a timeout in milliseconds and the method returns a promise which resolves after the timeout
 - otherwise, an exception is thrown
 
+```js
+// wait for selector
+await page.waitFor('.foo');
+// wait for 1 second
+await page.waitFor(1000);
+// wait for predicate
+await page.waitFor(() => !!document.querySelector('.foo'));
+```
+
+To pass arguments from node.js to the predicate of `page.waitFor` function:
+
+```js
+const selector = '.foo';
+await page.waitFor(selector => !!document.querySelector(selector), {}, selector);
+```
+
 Shortcut for [page.mainFrame().waitFor(selectorOrFunctionOrTimeout[, options[, ...args]])](#framewaitforselectororfunctionortimeout-options-args).
 
 #### page.waitForFunction(pageFunction[, options[, ...args]])
@@ -1581,6 +1597,14 @@ puppeteer.launch().then(async browser => {
   await browser.close();
 });
 ```
+
+To pass arguments from node.js to the predicate of `page.waitForFunction` function:
+
+```js
+const selector = '.foo';
+await page.waitForFunction(selector => !!document.querySelector(selector), {}, selector);
+```
+
 Shortcut for [page.mainFrame().waitForFunction(pageFunction[, options[, ...args]])](#framewaitforfunctionpagefunction-options-args).
 
 #### page.waitForNavigation(options)
@@ -2224,6 +2248,22 @@ This method behaves differently with respect to the type of the first parameter:
 - if `selectorOrFunctionOrTimeout` is a `number`, then the first argument is treated as a timeout in milliseconds and the method returns a promise which resolves after the timeout
 - otherwise, an exception is thrown
 
+```js
+// wait for selector
+await page.waitFor('.foo');
+// wait for 1 second
+await page.waitFor(1000);
+// wait for predicate
+await page.waitFor(() => !!document.querySelector('.foo'));
+```
+
+To pass arguments from node.js to the predicate of `page.waitFor` function:
+
+```js
+const selector = '.foo';
+await page.waitFor(selector => !!document.querySelector(selector), {}, selector);
+```
+
 #### frame.waitForFunction(pageFunction[, options[, ...args]])
 - `pageFunction` <[function]|[string]> Function to be evaluated in browser context
 - `options` <[Object]> Optional waiting parameters
@@ -2247,6 +2287,13 @@ puppeteer.launch().then(async browser => {
 });
 ```
 
+To pass arguments from node.js to the predicate of `page.waitForFunction` function:
+
+```js
+const selector = '.foo';
+await page.waitForFunction(selector => !!document.querySelector(selector), {}, selector);
+```
+
 #### frame.waitForSelector(selector[, options])
 - `selector` <[string]> A [selector] of an element to wait for
 - `options` <[Object]> Optional waiting parameters