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Mobile Usability – Custom Scrollbars

On mobile devices, Usability is everything.
Because of this, standard elements are often designed broader and larger.

Example of a 30px wide and 100px thumb custom scrollbar:

/*A custom scrollbar is configurable. 
Here, it is broader than the standard.
This way, it is easier to use on touchscreen 
or other small or mobile devices.*/

/* width */
::-webkit-scrollbar {
    width: 30px;
}

/* Track */
::-webkit-scrollbar-track {
    background: #f1f1f1;
}

/* Handle */
::-webkit-scrollbar-thumb {
    height: 100px!important;
    background: #888;
}

/* Handle on hover */
::-webkit-scrollbar-thumb:hover {
    background: #555;
}
/*end custom scrollbar*/
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Pixel sizes – Mobile – Screen – Resolution -Definition

This is a compilation from the Web. I do not know the original author. As I am good at compiling information, I think it will be useful, though.

In case you are the author of this and can prove it, please drop me a line so we can link to your content.

Standard Size Ratio Definition


16:9 Ratio

4:3 Ratio

3:2 Ratio

2:1 Ratio

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Delay function in JavaScript JS

The timeout function puts a thread to sleep, which is often NOT what you want:

function someFunction(param) {
    setTimeout(function () {
        if (param == -1) {
            console.log('Parameter is -1');
        }
    }, 2000);//2 sec delay
}

Instead with ECMA6 you can use the async/await syntax. 

const delay = ms => new Promise(res => setTimeout(res, ms));

const delayFunction = async () => {
  await delay(2000);
  console.log("[X] 2 sec delay.");
};

The Code looks like being synchronous while it is in fact asynchronous. This makes it easier to maintain. Plus you avoid a freeze in UIs in case you want to delay for the human eye in a UI…

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React Hook Component Conditional Rendering

The HTML is rerendered after click and displays the chosen content.

We use a stateful variable.

The stateful variable (here, a boolean):

const [status, setStatus] = useState(false);

The #useEffect method to react on variable state change:

useEffect(() => {
    ...
},[status]);

The methods for the buttons:

const handleClickStatus = () => setStatus(true);
const handleClickSomething = () => setStatus(false);

The returned HTML:

if (status === true) {
    return (
        <div>
            <Button variant="contained" 
                    color="primary" 
                    onClick={handleClickSomething}>
                Primary
            </Button>
            <Button variant="contained" 
                    color="secondary" 
                    onClick={handleClickStatus}>
                Secondary
            </Button>STATUS
        </div>
    );
} else {
    return (
        <div>
            <Button variant="contained" 
                    color="primary" 
                    onClick={handleClickContent}>
                Primary
            </Button>
            <Button variant="contained" 
                    color="secondary" 
                    onClick={handleClickStatus}>
                Secondary
            </Button>CONTENT
        </div>
    );
}
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Chrome – add insecure origins as secure

  1. Navigate to `chrome://flags/#unsafely-treat-insecure-origin-as-secure` in Chrome.
  2. Find and enable the `Insecure origins treated as secure` section (see below).
  3. Add any addresses you want to ignore the secure origin policy for. Remember to include the port number too (if required).
  4. Save and restart Chrome.
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React – use CSS depending on states (change class according to a variable’s state)

For this example I use React Hooks and a Component with a stateful variable.
When the variable is changed, the CSS class is changed accordingly.
The part in the component is automatically re-rendered on the fly.

//The variable is called 'active'. 
//This is an example. Choose any name.
const [active, setActive] = useState(0);

We use the constant #getStyle to return a CSS class name based on the variable.

    const getStyle = (input) => {
        if (input === active){
            // This example is freely chosen. 
            //button-active is the CSS class' name
            return "button-active";
        } else {
            return "button-inactive";
        }
    };

The return statement returns rendered HTML.

//The hard coded value 0 can be any dynamic 
//variable from JS or React, like one from the 
//props (Properties) object
return (
  <div className={getStyle(0)}>
  </div>
);
  • Stateful variable called ‚active‘
  • Const named #getStyle with an input parameter
  • render method returning HTML with a css class name
  • Input is provided to the #getStyle const
  • If the variable ‚active‘ is changed by the application somewhere, the HTML is re-rendered
  • The input is compared to the variable and the name of the CSS class returned
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CSS Grid Layout Example – Visible Structure – Easy Tutorial

4 Items, stretched with different sizes across a Matrix 4×4 grid.

You can see the Grid structure in the CSS in this example.

Picture:

CSS:

.item-a {
    grid-area: itemA;
    border: 1px solid violet;
}
.item-b {
    grid-area: itemB;
    border: solid 1px cyan;
}
.item-c {
    grid-area: itemC;
    border: solid 1px yellow;
}
.item-d {
    grid-area: itemD;
    border: solid 1px red;
}

.container {
    height: 100%;
    border: solid 1px green;
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
    grid-template-rows: 1fr 1fr 1fr 1fr;
    grid-template-areas:
            "itemA itemA itemC itemC"
            "itemA itemA itemC itemC"
            "itemA itemA itemD itemD"
            "itemA itemA itemD itemD";

HTML (in this example a React JS Grid):

return (
        <Grid className={"container"}>
            <Grid item className={"item-a"}></Grid>
            <Grid item className={"item-b"}></Grid>
            <Grid item className={"item-c"}></Grid>
            <Grid item className={"item-d"}></Grid>
        </Grid>
    );
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React – stateful variables and objects (State) & Hooks & Components

Imagine you want to re-render a Component when a variable changes its state.

Your Component:

function MyComponent(props) {

Your variable, a name:

const [name, setName] = useState("OLD NAME");

A #useEffect method to react to changes of that specific variable:

useEffect(()=>{
    alert('new name!');//a small alert to show you the effect immediately
    setName('NEW NAME');
}, [name]);

…and a return with that name being rendered:

return (
    <div className={"someFancyCssClass"}>{name}</div>            
);

Note that, in this example, the initial OLD NAME is immediately replaced.
Reason for it: we set the name during initialization in the const.

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Multiple Webapps with Docker Compose

  • Learn how to setup a custom network for your containers: container A talks to container B
  • Learn how to run multiple webapps inside Docker containers on different ports with Docker Compose

Download complete source code here

  • Create the network with $docker network create skynet
  • Run with $docker-compose up
  • Stop with $<Ctrl + C>
  • Clean up from time to time (beware, network will be deleted as well) with $docker system prune -a -f
  • access via http://localhost:8080/sample
  • access via http://localhost:8081/sample