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Global Variables

Oct 29, 2020LeifMessinger
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More JavaScript Posts

binomial coefficient

Nov 19, 2022CodeCatch

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const binomialCoefficient = (n, k) => {
if (Number.isNaN(n) || Number.isNaN(k)) return NaN;
if (k < 0 || k > n) return 0;
if (k === 0 || k === n) return 1;
if (k === 1 || k === n - 1) return n;
if (n - k < k) k = n - k;
let res = n;
for (let j = 2; j <= k; j++) res *= (n - j + 1) / j;
return Math.round(res);
};
binomialCoefficient(8, 2); // 28

Extracting components

Nov 19, 2022CodeCatch

0 likes • 2 views

function formatDate(date) {
return date.toLocaleDateString();
}
function Comment(props) {
return (
<div className="Comment">
<div className="UserInfo">
<img
className="Avatar"
src={props.author.avatarUrl}
alt={props.author.name}
/>
<div className="UserInfo-name">
{props.author.name}
</div>
</div>
<div className="Comment-text">{props.text}</div>
<div className="Comment-date">
{formatDate(props.date)}
</div>
</div>
);
}
const comment = {
date: new Date(),
text: 'I hope you enjoy learning React!',
author: {
name: 'Hello Kitty',
avatarUrl: 'https://placekitten.com/g/64/64',
},
};
ReactDOM.render(
<Comment
date={comment.date}
text={comment.text}
author={comment.author}
/>,
document.getElementById('root')
);

unzipWith() function

Nov 19, 2022CodeCatch

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const unzipWith = (arr, fn) =>
arr
.reduce(
(acc, val) => (val.forEach((v, i) => acc[i].push(v)), acc),
Array.from({
length: Math.max(...arr.map(x => x.length))
}).map(x => [])
)
.map(val => fn(...val));
unzipWith(
[
[1, 10, 100],
[2, 20, 200],
],
(...args) => args.reduce((acc, v) => acc + v, 0)
);
// [3, 30, 300]

Reddit Regex Comment Upvoter

May 17, 2021LeifMessinger

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//Upvotes comments according to a regex pattern. I tried it out on https://www.reddit.com/r/VALORANT/comments/ne74n4/please_admire_this_clip_precise_gunplay_btw/
//Known bugs:
//If a comment was already upvoted, it gets downvoted
//For some reason, it has around a 50-70% success rate. The case insensitive bit works, but I think some of the query selector stuff gets changed. Still, 50% is good
let comments = document.getElementsByClassName("_3tw__eCCe7j-epNCKGXUKk"); //Comment class
let commentsToUpvote = [];
const regexToMatch = /wtf/gi;
for(let comment of comments){
let text = comment.querySelector("._1qeIAgB0cPwnLhDF9XSiJM"); //Comment content class
if(text == undefined){
continue;
}
text = text.textContent;
if(regexToMatch.test(text)){
console.log(text);
commentsToUpvote.push(comment);
}
}
function upvote(comment){
console.log(comment.querySelector(".icon-upvote")); //Just showing you what it's doing
comment.querySelector(".icon-upvote").click();
}
function slowRecurse(){
let comment = commentsToUpvote.pop(); //It's gonna go bottom to top but whatever
if(comment != undefined){
upvote(comment);
setTimeout(slowRecurse,500);
}
}
slowRecurse();

retryPromise.js

Oct 20, 2023LeifMessinger

0 likes • 20 views

//Retries maxRetries number of times, meaning that if you have 0, then it'll run the function once.
async function retryPromise(promiseFn, maxRetries = 3, delayOffset = 0, delayRandomRange = 0) {
return new Promise((resolve, reject) => {
promiseFn()
.then(resolve, (error) => { //On error
if (maxRetries <= 0) {
return reject(error);
} else {
if(delayRandomRange * Math.random() + delayOffset < 1.0){
return retryPromise(promiseFn, maxRetries - 1, delayOffset, delayRandomRange).then(resolve, reject);
}else{
return new Promise((resolveTwo, rejectTwo) => {
setTimeout(() => {
return retryPromise(promiseFn, maxRetries - 1, delayOffset, delayRandomRange).then(resolveTwo, rejectTwo);
}, delayRandomRange * Math.random() + delayOffset);
}).then(resolve, reject);
}
}
});
});
}
//Tests for that function.
//Returns a function that will fail numTimes times, then will return aValue
function functionThatReturnsAFunctionThatFailsACoupleTimes(numTimes, aValue){
return async function(){
if(numTimes == 0){
return aValue;
}
numTimes--;
throw false;
};
}
const SMALL_NUMBER = 10;
function testTest(failNumberOfTimes){
let functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(failNumberOfTimes, true);
//Test my test
for(let i = 0; i < (failNumberOfTimes * 2); ++i){
function evalTest(val){
let testTestFailedReason = "";
if(val === undefined){
testTestFailedReason = "Test test returned undefined for some reason.";
}
if((i + 1) > failNumberOfTimes){
if(val === true){
//We're good
}else{
testTestFailedReason = "Test test didn't return true when it should have.";
}
}else{
if(val === false){
//We're good
}else{
testTestFailedReason = "Test test didn't return false when it should have.";
}
}
testTestFailedReason = testTestFailedReason || "Test test passed test case";
console.log(testTestFailedReason, "at index", i, "where the function returned", val);
}
functionThatFailsACoupleTimes().then(evalTest, evalTest)
};
}
testTest(SMALL_NUMBER);
let testCaseCounter = 1;
const throwsNoError = [
(val)=>{
if(val == true){
console.log("Passed test case " + (testCaseCounter++));
}else{
console.error("Unexpected return value", val);
}
},
()=>{
console.error("It wasn't supposed to fail!")
}
]
const throwsError = [
(val)=>{
console.error("It wasn't supposed to succeed!", val);
},
(val)=>{
if(val == false){
console.log("Passed test case " + (testCaseCounter++));
}else{
console.error("Unexpected return value", val);
}
}
];
//Runs SMALL_NUMBER times, because SMALL_NUMBER - 1 is the number of retries after the first one
let functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);
retryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 1).then(...throwsNoError)
functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);
//Runs SMALL_NUMBER - 1 times, because SMALL_NUMBER - 2 is the number of retries after the first one
retryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 2).then(...throwsError)
//Testing the delay. You'll have to wait a bit too.
functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);
//Runs SMALL_NUMBER times, because SMALL_NUMBER - 1 is the number of retries after the first one
retryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 1, 500, 500).then(...throwsNoError)
functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);
//Runs SMALL_NUMBER - 1 times, because SMALL_NUMBER - 2 is the number of retries after the first one
retryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 2, 500, 500).then(...throwsError)

permutations

Nov 19, 2022CodeCatch

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const permutations = arr => {
if (arr.length <= 2) return arr.length === 2 ? [arr, [arr[1], arr[0]]] : arr;
return arr.reduce(
(acc, item, i) =>
acc.concat(
permutations([...arr.slice(0, i), ...arr.slice(i + 1)]).map(val => [
item,
...val,
])
),
[]
);
};
permutations([1, 33, 5]);
// [ [1, 33, 5], [1, 5, 33], [33, 1, 5], [33, 5, 1], [5, 1, 33], [5, 33, 1] ]