Understanding website paywall approaches

Subscription paywalls are becoming more and more common on a number of news and other sites. Assuming that the sites are using JavaScript and/or CSS approaches in the page to popup floating DIVs obscuring the content of the page, these are surprisingly easy to bypass if you know what to look for.

There’s many other articles (e.g. here) discussing these approaches and this is not intended to be an exclusive list, but here’s a few useful observations:

  • Adding a trailing ‘.’ to the domain name works on a surprising number of sites (Google if you’re interested why this works)
  • If you’ve tried this and you’re still getting a popup obscuring content on the page, using your browser’s developer tools, use the ‘select element’ feature to click on a floating DIV in the page and then update the CSS to style=”display:none” is also effective. If there’s other script in the place which is adding the CSS to the DIV, right click the DIV and just select the delete element option also works
  • Some sites use a combination of approaches. Often script or CSS to disable scrolling the page underneath a floating DIV is also used, so if you’ve removed the DIV but now you can’t scroll the content, look at the style on the body. If there’s an “overflow:hidden” style, remove it, or change it to “overflow:auto”

Interrelated personal side projects can be a goldmine of learning opportunities

Some people struggle to find ideas for working on side/personal software development projects for learning (and fun!). I’ve kept a running list of ideas in an online notebook and if I’m struggling for an idea for a new project I refer back to this list.

Over the past couple of years I stumbled across a series of inter-related projects that’s been a goldmine of learning opportunities, from frontend to backend to serverless.

This series of projects started with a question “Can you solve a problem without understanding the problem?”. tl;dr? No. The problem for this activity was solving Sudoku puzzles, and you can read more about this here:

This lead to the next step, researching more about exact cover problems, and how they can be solved with well established algorithms:

After building an implementation of Donald Knuth’s Algorithm X, I packaged it up as an AWS Lambda, and then built a React frontend for it:

I have one other project in progress for the frontend, replacing Flux with Redux. I’m still working on that one.

After building my solver and the frontend, I starting thinking about how to generate new puzzles. This is in progress here: https://github.com/kevinhooke/sudoku-generator

If you’re generating new puzzles you also need a way to grade the difficulty of puzzles. The unusual thing about this is there’s no established algorithm for grading the complexity of Sudoku puzzles, they’re typically graded by applying human solving techniques, so this led to this: https://github.com/kevinhooke/sudoku-human-grader

This string of related projects has kept me busy of the past couple of years. Not every idea will lead to a series of related projects like this, but if you can find an idea that does, it will keep you busy with plenty of problems to solve and many learning opportunities.

React Redux cheatsheet

This is my summary of the bare minimum steps as a quick-ref cheatsheet for adding Redux to an existing React app. This is just some notes for future reference. If you’re looking for tutorials, take a look at:

Here’s my quickref:

npm install --save react-redux

Add Redux devtools for Chrome (see here):

npm install --save-dev redux-devtools-extension

Wrap <Provider> around root Component to share the Store with all child components:

import { Provider } from 'react-redux'
import store from './store'

<Provider store={store}>
  <App>
</Provider>

Implement mapStateToProps and mapDispatchToProps to pass store and dispatch() as props to each Component, and call connect() to connect each Component with your Redux Store:

const mapStateToProps = (state) => {
  return {
    yourcomponent: state.yourcomponent
  }
}
export default connect(
  mapStateToProps,
  mapDispatchToProps
)(YourComponent)

Create a Store:

import { createStore } from 'redux';
import { devToolsEnhancer } from 'redux-devtools-extension';
let store = createStore(yourReducer, devToolsEnhancer());
export default store;

Create reducers for Store – here’s an example that take the the value of a label from the passed action payload and sets it in the Store – remember the state of the store is always treated as immutable, so always create a new copy of the modified state, here using Object.assign():

function labelReducer(state = initialState, action) {
  switch (action.type) {
    case 'CHANGE_LABEL':
      return Object.assign( {},{ labelValue : action.payload 
    } );
    default:
      return state;
    }
}

Implement an action creator that builds an Action object that requests changes to the Store – each action has a type and a payload:

export function changeLabel(payload) {
  return { type: "LABLE_CHANGE", payload }
};

Implement mapDispatchToProps – you can either build the Action object yourself here, or call an Action creator like the above example:

function mapDispatchToProps(dispatch) {
return {
  changeLabel: labelValue => 
    dispatch(changeLabel(labelValue))
  };
}

Pass mapDispatchToProps to your connect() call shown earlier.

As a comparison, here’s a simple React app using Flux:

https://github.com/kevinhooke/SimpleReactFluxExample

… and here’s the same app converted to use Redux:

https://github.com/kevinhooke/SimpleReactReduxExample

Done!

React and Redux error: “_react.default.createContext is not a function”

I’m adding Redux to an existing React app, converting from Flux to Redux. After wrapping my root component with the <Provider> I got this error and the app doesn’t initialize:

_react.default.createContext is not a function

Doing a quick search found this post suggesting I’ve got a mismatch in versions between newest Redux versions and possibly older versions of React. This is possible as I’m updating an older React app I put together a couple of years ago. Quick way to test this, remove React and react-dom and add them back again.

Right now I have:

"react": "^15.4.1",
"react-dedux": "^0.4.0-beta.4",
"react-dom": "^15.4.1",
"react-redux": "^7.2.0"

Removed React and react-dom and added back latest versions:

"react": "^16.13.1",
"react-dedux": "^0.4.0-beta.4",
"react-dom": "^16.13.1",
"react-redux": "^7.2.0"

Restated my app, fixed!