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7-subscriber.js
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71 lines (60 loc) · 1.55 KB
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'use strict';
class Observable {
constructor(subscribe) {
this.observers = [];
this.operators = [];
if (subscribe) setTimeout(subscribe, 0, this);
}
subscribe(observer) {
this.observers.push(observer);
return this;
}
pipe(...args) {
this.operators.push(...args);
const destination = new Observable();
this.subscribe((data) => destination.next(data));
return destination;
}
next(data) {
if (this.observers.length === 0) return;
for (const operator of this.operators) {
if (operator.name === 'filter') {
if (!operator.fn(data)) return;
}
if (operator.name === 'map') {
data = operator.fn(data);
}
}
for (const observer of this.observers) {
observer(data);
}
}
}
const filter = (predicate) => ({ name: 'filter', fn: predicate });
const map = (callback) => ({ name: 'map', fn: callback });
const randomChar = () =>
String.fromCharCode(Math.floor(Math.random() * 25 + 97));
const source = new Observable((subscriber) => {
setInterval(() => {
const char = randomChar();
subscriber.next(char);
}, 200);
});
const destination = source.pipe(
filter((char) => !'aeiou'.includes(char)),
map((char) => char.toUpperCase()),
);
const createObserver = () => {
let count = 0;
return (char) => {
process.stdout.write(char);
count++;
if (count > 50) {
process.stdout.write('\n');
process.exit(0);
}
};
};
const observer = createObserver();
destination.subscribe(observer);
console.dir({ observer, source, destination });