Q111. Why do we need callbacks?
The callbacks are needed because javascript is an event driven language. That means instead of waiting for a response, javascript will keep executing while listening for ...
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Q112. How do you access props in attribute quotes?
React (or JSX) doesn't support variable interpolation inside an attribute value. The below representation won't work: ```jsx harmony ``` But you can put any JS expression...
Q113. What is a callback hell?
Callback Hell is an anti-pattern with multiple nested callbacks which makes code hard to read and debug when dealing with asynchronous logic. The callback hell looks like...
Q114. What is React proptype array with shape?
If you want to pass an array of objects to a component with a particular shape then use `React.PropTypes.shape()` as an argument to `React.PropTypes.arrayOf()`. ```javasc...
Q115. What are server-sent events?
Server-sent events (SSE) is a server push technology enabling a browser to receive automatic updates from a server via HTTP connection without resorting to polling. These...
Q116. How to conditionally apply class attributes?
You shouldn't use curly braces inside quotes because it is going to be evaluated as a string. ```jsx harmony ``` Instead you need to move curly braces outside (don't forg...
Q117. How do you receive server-sent event notifications?
The EventSource object is used to receive server-sent event notifications. For example, you can receive messages from server as below, ```javascript if (typeof EventSourc...
Q118. What is the difference between React and ReactDOM?
The `react` package contains `React.createElement()`, `React.Component`, `React.Children`, and other helpers related to elements and component classes. You can think of t...
Q119. How do you check browser support for server-sent events?
You can perform browser support for server-sent events before using it as below, ```javascript if (typeof EventSource !== "undefined") { // Server-sent events supported. ...
Q120. Why ReactDOM is separated from React?
The React team worked on extracting all DOM-related features into a separate library called _ReactDOM_. React v0.14 is the first release in which the libraries are split....