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feat: added polyfill solution for setTimeout in INTERVIEW_QUESTIONS #142

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Merged
akshitagupta15june merged 2 commits into from
Oct 2, 2022
Merged

feat: added polyfill solution for setTimeout in INTERVIEW_QUESTIONS #142

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c3f1253
feat: added polyfill for setTimeout solution in INTERVIEW_QUESTIONS
imanshu03 Oct 2, 2022
1f64b51
fix: typo error
imanshu03 Oct 2, 2022
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73 changes: 73 additions & 0 deletions INTERVIEW_QUESTION/Polyfills/setTimeout.js
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Original file line number Diff line number Diff line change
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// NOTE: Run this script in browser snippets as running on Node.js environment will throw `window is not defined` error.


(function () {
// Object to store registered timers
const timerCallbackMap = {};


// Function to generate unique ids for a particular callback
function generateId() {
const chars = "12356ABCDEF";
let key = "";
for (let i = 0; i < 6; i++) {
const idx = Math.floor(Math.random() * chars.length);
key += chars[idx];
}
return key;
}


// Function to be called when browser is idle to check if any callback execution time is pass the current time
function check() {
if (timerCallbackMap.size === 0) return;

for (let timerId in timerCallbackMap) {
const now = Date.now();
if (now > timerCallbackMap[timerId].execTime) {
timerCallbackMap[timerId].callback();
window.myClearTimeout(timerId);
}
}

requestIdleCallback(check);
}


// Polyfill for setTimeout
window.mySetTimeout = function (callback, delay = 0) {
// check if arguments are of correct type
if (typeof callback !== "function") throw new Error("callback should be a function");
if (typeof delay !== "number" || delay < 0)
throw new Error("delay should be a positive number");


// generate unique id for callback
const timerId = generateId();


// store the callback and set its execution time as current epoch value + delay in milliseconds
timerCallbackMap[timerId] = {
callback,
execTime: Date.now() + delay
};

// queue the check function to be called when browser is idle
if (Object.keys(timerCallbackMap).length === 1) requestIdleCallback(check);

return timerId;
};


// Polyfill for clearTimeout
window.myClearTimeout = function (timerId) {
if (timerCallbackMap[timerId]) {
delete timerCallbackMap[id];
}
};
})();

const id = mySetTimeout(() => {
console.log("Hello");
}, 2000);