Implementing and using the basic promise

promise.js

/**
 * @author Aashish Chaubey
 * @link https://github.com/aashish-chaubey
 */

/**
 * First Create a Promise my implementing it with a `new` keyword
 * Do all the heavy weight operations in the promise
 * Store the promise in a variable
 */

let myPromise = new Promise((resolve, reject) => {
    setTimeout(() => {
        let rand = Math.random()
        console.log(rand)
        if(rand < 0.5) {
            resolve("The Random Value is less than 0.5")
        } else {
            reject("Random Value is greater then 0.5")
        }
    }, 2000)
})

/**
 * Execute the promise
 * Call the `.then()` and `.catch()` for the resolve and rejected values respectively
 */

myPromise
.then(resp => {
    console.log(resp);
})
.catch(err => {
    console.log(err);
})

Important to note is that:

Callback saves us from callback hell in chaining and thus making the code more readable