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simple implementation for chain #13

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simple implementation for chain #13

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5acccd6
simple implementation
stillgg Mar 18, 2024
3c82445
add error handling
stillgg Mar 18, 2024
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63 changes: 63 additions & 0 deletions JavaScript/5c-chain.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,63 @@
const wrapAsync =
(fn) =>
(...args) =>
setTimeout(() => fn(...args), Math.random() * 1000);

const readConfig = wrapAsync((data, callback) => {
console.log("data - ", data);
console.log("read config");

callback(null, data);
});

const selectFromDb = wrapAsync((query, callback) => {
console.log("query - ", query);
console.log("select from db");

callback(null, { cat: "Evgeniy" });
});

const getHttpPage = wrapAsync((page, callback) => {
console.log("page - ", page);
console.log("Page retrieved");

callback(null, { page: "<html>hello world!</html>" });
});

const chain = () => {
const stack = [];

const executor = () => {
let result = () => null;

const len = stack.length;

for (let i = len - 1; i >= 0; i--) {
const [fn, args] = stack.pop();

const prev = result;

result = (err, data) => {
if (err) return console.error({ err });
fn(...args, prev);
};
}

result();
};

executor.do = (cb, ...args) => {
stack.push([cb, args]);

return executor;
};

return executor;
};

const startChain = chain()
.do(readConfig, "myConfig")
.do(selectFromDb, "select * from cities")
.do(getHttpPage, {});

startChain();