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CodeCatchCrasher

Feb 11, 2021LeifMessinger
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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

retryPromise.js

Oct 20, 2023LeifMessinger

0 likes • 18 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)

greatest common denominator

Nov 19, 2022CodeCatch

0 likes • 0 views

const gcd = (...arr) => {
const _gcd = (x, y) => (!y ? x : gcd(y, x % y));
return [...arr].reduce((a, b) => _gcd(a, b));
};
gcd(8, 36); // 4
gcd(...[12, 8, 32]); // 4

Horizontal legend (d3.js)

Dec 17, 2024shaiRos

0 likes • 2 views

const rectSize = 15; // Size of the color box
const spacing = 5; // Space between legend items
let legend = canvas.append('g').attr('class','chart-legend')
.attr('transform', `translate(${0}, ${height + 3})`);
// Sample data for the legend
const legendData = [
{ label: 'low', color: '#1f77b4' },
{ label: 'medium', color: '#ff7f0e' },
{ label: 'high', color: '#2ca02c' },
{ label: 'very high', color: '#2ca02c' }
];
legend.selectAll('g')
.data(legendData)
.join('g')
.attr('class', 'legend-item')
.each(function (d, i) {
const legendItem = d3.select(this);
console.log(d.label)
console.log(d.label?.length)
let labelWidth = (d.label.length * 5) + 7 + 15
var bbox = legendItem.node().getBBox()
var width = bbox.width
console.log(width)
// Add rectangle for color
legendItem.append('rect')
.attr('width', rectSize)
.attr('height', rectSize)
.attr('fill', d.color);
// Add label
legendItem.append('text')
.attr('x', rectSize + spacing) // Position text to the right of the rectangle
.attr('y', rectSize / 2) // Align text vertically with the rectangle
.attr('dy', '.35em') // Adjust vertical alignment
.attr('text-anchor', 'start') // Align text to the start
.text(d.label)
.attr('fill', 'black'); // Optional: Text color
// legendItem.attr('transform', `translate(${i * (rectSize + spacing + labelWidth)}, 0)`) // Position each item horizontally
});
const legendItems_spacing = 12
var legendLength = 0
legend.selectAll('.legend-item').each(function(d,i) {
d3.select(this).attr('transform',function() {
var bbox = d3.select(this).node().getBBox()
var width = bbox.width
// if (width == 0) width = (d.text.length * 5) +15 // not in dom yet
let startingPosition = 0
if (i > 0) {
startingPosition = legendLength
}
legendLength += width + legendItems_spacing
// return `translate(${xx - (width + 30)},0$)`
return `translate(${startingPosition},0)`
})
})

Scrape twitter

Sep 2, 2023LeifMessinger

0 likes • 10 views

//Allegedly never tested on the twitter website
function scrapeScreen(){
let articles = Array.from(document.getElementsByTagName("article"));
let results = [];
for(let tweet of articles){
const isAnAd = Array.from(tweet.querySelectorAll("span")).map((e)=>e.textContent).includes("Ad");
if(isAnAd){
//console.log(tweet, "is an ad. Skipping...");
continue;
}
const userName = tweet.querySelector("[data-testid='User-Name'] > div:nth-child(2) > div > div")?.textContent;
const tweetContent = tweet.querySelector("[data-testid='tweetText']")?.textContent;
const timeStamp = tweet.querySelector("time")?.getAttribute("datetime");
const tweetLink = tweet.querySelector("time")?.parentElement?.getAttribute("href");
if((!userName) || (!tweetContent)) continue;
results.push({
username: userName,
tweetText: tweetContent,
timeStamp: timeStamp,
tweetLink: tweetLink
});
}
return results;
}
let scraped = scrapeScreen();
setInterval(()=>{
scraped = scraped.concat(
scrapeScreen().filter((tweet)=>{
for(let scrapedTweet of scraped){
if(scrapedTweet.username == tweet.username && scrapedTweet.tweetText == tweet.tweetText) return false;
}
return true;
})
);
}, 500); //Scrape everything on the screen twice a second
window.scrollIntervalId = setInterval(function(){
window.scrollBy(0, 1000);
}, 500); //Scroll for me
//http://bgrins.github.io/devtools-snippets/#console-save
(function(console){
console.save = function(data, filename){
if(!data) {
console.error('Console.save: No data')
return;
}
if(!filename) filename = 'console.json'
if(typeof data === "object"){
data = JSON.stringify(data, undefined, '\t')
}
var blob = new Blob([data], {type: 'text/json'}),
e = document.createEvent('MouseEvents'),
a = document.createElement('a')
a.download = filename
a.href = window.URL.createObjectURL(blob)
a.dataset.downloadurl = ['text/json', a.download, a.href].join(':')
e.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null)
a.dispatchEvent(e)
}
})(console)
setTimeout(()=>{
clearTimeout(window.scrollIntervalId);
delete window.scrollIntervalId;
console.save(scraped, "TwitterScrape" + Date.now() + ".json");
}, 60 * 1000 * 20); //Twenty minutes

native data structures

Nov 19, 2022CodeCatch

0 likes • 0 views

const nums = [1, 2, 3];
const strs = Array.from('est');
nums.push(6);
nums.push(4, 9);
strs.unshift('t');
nums.length; // 6
nums[nums.length - 1]; // 9
strs[0]; // 't'
strs[2]; // 's'
nums.slice(1, 3); // [2, 3]
nums.map(n => n * 2); // [2, 4, 6, 12, 8, 18]
nums.filter(n => n % 2 === 0); // [2, 6, 4]
nums.reduce((a, n) => a + n, 0); // 25
strs.reverse(); // ['t', 's', 'e', 't']
strs.join(''); // 'test'
const nums = new Set([1, 2, 3]);
nums.add(4);
nums.add(1);
nums.add(5);
nums.add(4);
nums.size; // 5
nums.has(4); // true
nums.delete(4);
nums.has(4); // false
[...nums]; // [1, 2, 3, 5]
nums.clear();
nums.size; // 0
const items = new Map([
[1, { name: 'John' }],
[2, { name: 'Mary' }]
]);
items.set(4, { name: 'Alan' });
items.set(2, { name: 'Jeff' });
items.size; // 3
items.has(4); // true
items.get(2); // { name: 'Jeff' }
items.delete(2);
items.size; // 2
[...items.keys()]; // [1, 4]
[...items.values()]; // [{ name: 'John' }, { name: 'Alan' }]
items.clear();
items.size; // 0