Using React Contexts we can communicate across a hierarchy of Components. To understand this, think of a widget represented by a View component which has lots of child view components. You might use/re-use this component and want to pass certain properties or attributes that are relevant to different child components affecting the overall state (look and behaviour) of the main component in combination. Now one way to achieve this is by using props. But imagine passing an attribute all the way down from the parent to a child at the 5th level in the hierarchy. At every component level the property passed from the parent will have to be accessed (this.props.propName) and further passed down. This can get really messy. So let’s see how contexts can be used to pass data across components in a much elegant manner.
Tag: javascript
Remove a Mounted React Component with React.unmountComponentAtNode()
While going through the codebase of React Bootstrap (for some reason), I came across an interesting implementation of a “React playground”. The code behind the playground is in ReactPlayground.js. I found this piece of interesting code there:
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React Integrating Routing to Material UI’s Left Nav (or Other Components)
Working with the React Material UI and trying to make routing work (or even understand how it works) with clicks on the LeftNav item items ? It’s actually quite simple once you get a hang of it. I’ll show you the code and explain the logic behind how on clicking navigation links in LeftNav you navigate to different pages/URLs in your app/website (in a snap). We’ll be using React Router, Material UI and obviously, ReactJS itself. I’ve also uploaded the code to Github.
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React Material UI – Open Left Menu (Navigation Drawer) on AppBar’s Hamburger Icon Click
This is more of a quick tip on a Material UI integration than a detailed article. We’ll see how to open the LeftNav component on clicking the AppBar’s left icon (hamburger menu icon). Unfortunately the documentation as of now doesn’t show the ReactJS code for this. Obviously it’s not too hard to figure it out either if you go through the website’s source itself on Github.
JavaScript Copy to ClipBoard (without Flash) using Cut and Copy Commands with document.execCommand()
Using the cut and copy commands via document.execCommand(), a text selection can be cut or copied to the user’s clipboard in Chrome 43+, Opera 29+ and IE 10+. This means we can now cater to a part of our web userbase with the copy to clipboard feature without using Flash. Let’s write some code to see these commands in action.
JavaScript document.execCommand() Web Method
The JS document.execCommand() method is quite interesting. It can be used to execute certain commands to play with an editable region that is achieved either via the contenteditable attribute or when the HTML document (of the main window or some iframe window) has been switched to designMode using this code:
document.designMode = 'on'; // or 'off' // or for an iframe iframeNode.contentDocument.designMode = 'on'; // or 'off')
Infact try the first snippet right in dev tools and see what happens 🙂
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QuickTip: Store Undefined and Null in Class/Table Rows on Parse.com
Update: Parse is shutting down. So you should start migrating.
I’ve been working on an Android app backed by Parse.com to make my development process faster and easier. So while coding the app I made a decision to have 2 classes (tables) called Conversations and User (exists by default). Conversations has a field called userId that should essentially store the objectId from User class. But some conversations are created by guest so for those records I decided to store NULL or “nothing” (undefined) under the userId column rather than Pointers which is what the column type is.
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