Lockscreen

By adamlubek

This recipe demonstrates RxJS implementation of lockscreen functionality (known for example from smartphones).

Ultimate RxJS

Example Code

( StackBlitz )

Lockscreen

index.ts

/*
Use mouse to 'swipe' across the lock pad (hold mouse button and swipe :) ).
Pad will turn green if password is correct or red if password is incorrect.
You can set password to whatever sequence you like.
*/
// RxJS v6+
import { from, fromEvent, Subject, merge, pipe } from 'rxjs';
import {
switchMap,
takeUntil,
repeat,
tap,
map,
throttleTime,
distinctUntilChanged,
filter,
toArray,
sequenceEqual,
pluck
} from 'rxjs/operators';
import {
displaySelectedNumbersSoFar,
markTouchedPad,
pads,
resetPasswordPad,
setResult
} from './dom-updater';
const sub = new Subject();
const expectedPasswordUpdate$ = fromEvent(
document.getElementById('expectedPassword'),
'keyup'
).pipe(
map((e: any) => e.target.value),
tap(pass => sub.next(pass.split('').map(e => parseInt(e))))
);
let expectedPassword = [1, 2, 5, 2];
const expectedPassword$ = sub.pipe(tap((v: any) => (expectedPassword = v)));
const takeMouseSwipe = pipe(
// take mouse moves
switchMap(_ => fromEvent(document, 'mousemove')),
// once mouse is up, we end swipe
takeUntil(fromEvent(document, 'mouseup')),
throttleTime(50)
);
const checkIfPasswordMatch = password =>
from(password).pipe(sequenceEqual(from(expectedPassword)));
const getXYCoordsOfMousePosition = ({ clientX, clientY }: MouseEvent) => ({
x: clientX,
y: clientY
});
const findSelectedPad = v =>
pads.find(
r => v.x > r.left && v.x < r.right && v.y > r.top && v.y < r.bottom
);
const getIdOfSelectedPad = pipe(
filter(v => !!v),
pluck('id'),
distinctUntilChanged()
);
const actualPassword$ = fromEvent(document, 'mousedown').pipe(
// new stream so reset password pad and take swipe until mouse up
tap(resetPasswordPad),
takeMouseSwipe,
// as we swipe, we mark pads as touched and display selected numbers
map(getXYCoordsOfMousePosition),
map(findSelectedPad),
getIdOfSelectedPad,
tap(markTouchedPad),
tap(displaySelectedNumbersSoFar),
// we need an array of numbers from current swipe which we can pass to checkIfPasswordMatch
toArray(),
// on mouse up (swipe end), switchMap to new stream to check if password match
switchMap(checkIfPasswordMatch),
tap(setResult),
// takeUntil inside takeMouseSwipe terminated stream so we repeat from beginning (mousedown)
repeat()
);
merge(expectedPassword$, expectedPasswordUpdate$, actualPassword$).subscribe();

dom-updater.ts

const createPadObject = (id, rectange) => ({
id: id,
left: rectange.left,
right: rectange.right,
top: rectange.top,
bottom: rectange.bottom
});
const setResultText = text =>
(document.getElementById('result').innerText = text);
const setPasswordPads = color =>
Array.from(document.querySelectorAll('.cell')).forEach(
(v: HTMLElement) => (v.style.background = color)
);
const getPad = id => document.getElementById(`c${id}`);
export const pads = Array.from({ length: 9 }, (_, n) => n + 1).map(v =>
createPadObject(v, getPad(v).getBoundingClientRect())
);
export const markTouchedPad = v => {
const pad = getPad(v);
pad.style.background = 'lightgrey';
if (!pad.animate) return; //animate does not work in IE
const animation: any = [
{ transform: 'scale(0.9)' },
{ transform: 'scale(1)' }
];
const animationOptions = {
duration: 300,
iterations: 1
};
pad.animate(animation, animationOptions);
document.getSelection().removeAllRanges();
};
export const setResult = result => {
setPasswordPads(result ? 'MediumSeaGreen' : 'IndianRed');
setResultText('Password ' + (result ? 'matches :)' : 'does not match :('));
};
export const displaySelectedNumbersSoFar = v =>
(document.getElementById('result').textContent += v);
export const resetPasswordPad = () => {
setResultText('');
setPasswordPads('gray');
};

html

<style>
.grid {
border-spacing: 2px;
}
.cell {
width: 50px;
height: 50px;
background: grey;
display: table-cell;
border-radius: 50%;
transform: scale(0.5);
text-align: center;
vertical-align: middle;
color: white;
}
.pulse div {
animation-name: pulse;
animation-duration: 2s;
animation-iteration-count: infinite;
}
@keyframes pulse {
from {
transform: scale(1);
}
50% {
transform: scale(0.99);
}
to {
transform: scale(1);
}
}
</style>
Expected Password:
<input id="expectedPassword" value="1252" />
<hr />
Password:
<div class="grid pulse">
<div>
<div class="cell" id="c1">1</div>
<div class="cell" id="c2">2</div>
<div class="cell" id="c3">3</div>
</div>
<div>
<div class="cell" id="c4">4</div>
<div class="cell" id="c5">5</div>
<div class="cell" id="c6">6</div>
</div>
<div>
<div class="cell" id="c7">7</div>
<div class="cell" id="c8">8</div>
<div class="cell" id="c9">9</div>
</div>
</div>
<div id="result"></div>

Operators Used