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geometric progression

0 likes • Nov 19, 2022 • 0 views
JavaScript
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More JavaScript Posts

Extracting components

0 likes • Nov 19, 2022 • 2 views
JavaScript
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')
);

Monotonic Array

0 likes • Nov 19, 2022 • 2 views
JavaScript
// Time Complexity : O(N)
// Space Complexity : O(1)
var isMonotonic = function(nums) {
let isMono = null;
for(let i = 1; i < nums.length; i++) {
if(isMono === null) {
if(nums[i - 1] < nums[i]) isMono = 0;
else if(nums[i - 1] > nums[i]) isMono = 1;
continue;
}
if(nums[i - 1] < nums[i] && isMono !== 0) {
return false;
}
else if(nums[i - 1] > nums[i] && isMono !== 1) {
return false;
}
}
return true;
};
let nums1 = [1,2,2,3]
let nums2 = [6,5,4,4]
let nums3 = [1,3,2]
console.log(isMonotonic(nums1));
console.log(isMonotonic(nums2));
console.log(isMonotonic(nums3));

drag and drop uploader

0 likes • Nov 18, 2022 • 0 views
JavaScript
const dragAndDropDiv = editor.container;
dragAndDropDiv.addEventListener('dragover', function(e) {
e.stopPropagation();
e.preventDefault();
e.dataTransfer.dropEffect = 'copy';
});
dragAndDropDiv.addEventListener("drop",function(e){
// Prevent default behavior (Prevent file from being opened)
e.stopPropagation();
e.preventDefault();
const files = e.dataTransfer.items; // Array of all files
console.assert(files.length >= 1);
if (files[0].kind === 'file') {
var file = e.dataTransfer.items[0].getAsFile();
const fileSize = file.size;
const fileName = file.name;
const fileMimeType = file.type;
reader = new FileReader();
reader.onloadend = function(){
editor.setValue(reader.result);
}
reader.readAsText(file);
}else{
//Maybe handle if text is dropped
console.log(files[0].kind);
}
});

retryPromise.js

0 likes • Oct 20, 2023 • 12 views
JavaScript
//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)

Convert data to yyyy mm dd format

0 likes • Nov 19, 2022 • 1 view
JavaScript
// `date` is a `Date` object
const formatYmd = date => date.toISOString().slice(0, 10);
// Example
formatYmd(new Date()); // 2020-05-06

deep merge objects

0 likes • Nov 19, 2022 • 2 views
JavaScript
const deepMerge = (a, b, fn) =>
[...new Set([...Object.keys(a), ...Object.keys(b)])].reduce(
(acc, key) => ({ ...acc, [key]: fn(key, a[key], b[key]) }),
{}
);
deepMerge(
{ a: true, b: { c: [1, 2, 3] } },
{ a: false, b: { d: [1, 2, 3] } },
(key, a, b) => (key === 'a' ? a && b : Object.assign({}, a, b))
);
// { a: false, b: { c: [ 1, 2, 3 ], d: [ 1, 2, 3 ] } }