1// JS Tip of the Day
2// Promise.allSettled method
3
4const heroPromises = Promise.allSettled([
5  Promise.resolve('Batman'),
6  Promise.resolve('Superman'),
7  Promise.reject('Spiderman is not a DC Hero!')
8]);
9
10heroPromises.then(promises => {
11  promises.forEach(item => console.log(item));
12});
13
14// {status: "fulfilled", value: "Batman"}
15// {status: "fulfilled", value: "Superman"}
16// {status: "rejected", reason: "Spiderman is not a DC Hero!"}

1// JS Tip of the Day
2// Promise.all method
3
4const heroPromises = Promise.allSettled([
5  Promise.resolve('Batman'),
6  Promise.resolve('Superman')
7]);
8
9const anotherHeroPromises = Promise.allSettled([
10  Promise.resolve('Batman'),
11  Promise.reject('Spiderman is not a DC Hero!')
12])
13
14setTimeout(function() {
15  console.log(heroPromises);
16  // Promise { <state>: 'fullfilled', <value>: Array[2] }
17  
18  console.log(anotherHeroPromises);
19  // Promise { <state>: 'rejected', <reason>: 'Spiderman is not a DC Hero!' }
20});

1// JS Tip of the Day
2// Create an object with the number of occurrences of the array elements
3
4const occurrences = arr => {
5  return arr.reduce((obj, item) => {
6    obj[item] = obj[item] ? obj[item] + 1 : 1;
7    return obj;
8  }, {});
9}
10
11occurrences(['Batman', 'Superman', 'Batman', 'Cyborg']); 
12// { Batman: 2, Superman: 1, Cyborg: 1 }
13

1// JS Tip of the Day
2// Using Function.length 
3
4function myFunctionWithoutParams() {}
5console.log(myFunctionWithoutParams.length); // 0
6
7function myFunctionWithOneParam(firstParam) {}
8console.log(myFunctionWithOneParam.length); // 1
9
10function myFunctionWithTwoParams(firstParam, secondParam) {}
11console.log(myFunctionWithTwoParams.length); // 2
12
13// rest parameter is not counted
14function myFunctionWithRest(firstParam, secondParam, ...rest) {}
15console.log(myFunctionWithRest.length); // 2 
16
17// only parameters before the first one with a default value is counted
18function myFunctionWithDefault(firstParam, secondParam = '', thirdParam) {}
19console.log(myFunctionWithDefault.length); // 1 

1// JS Tip of the Day
2// Singleton Pattern Class (without ES Module)
3
4class Singleton {
5  constructor() {
6    if (!Singleton.instance) {
7      console.log('Create singleton instance');
8      Singleton.instance = this;
9    }
10    console.log('Get singleton instance');
11    return Singleton.instance;
12  }
13}
14
15const singletonA = new Singleton(); 
16// Create singleton instance
17// Get singleton instance
18const singletonB = new Singleton(); 
19// Get singleton instance
20
21console.log(singletonA === singletonB); // true