Created
March 25, 2022 21:45
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Promises example
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// java script is asynchronous | |
// it is not synchronous | |
// it is asynchronous | |
// it is not blocking | |
// const a = "" | |
// const a = 0 | |
// const a = {} | |
// const a = [] | |
// const a = [""] | |
// const a = [0] | |
// const a = () => {} | |
// function a(){} | |
// how to declare a promise | |
// new Promise() means initializing a promiseObj object | |
// = means assigning a value to a promiseObj object | |
// const promiseObj = new Promise((resolve, reject) => { | |
// // generate a random 2 digit positive integer | |
// const randomNum = Math.floor(Math.random() * 100) | |
// console.log(randomNum, "randomNum"); | |
// if (randomNum % 2 === 0) { | |
// resolve(randomNum) | |
// } | |
// else { | |
// reject("Promise is rejected, putin") | |
// } | |
// }) | |
// promiseObj.then((res) => { | |
// console.log(res, "Promise is resolved"); | |
// }).catch((err) => { | |
// console.error(err); | |
// }) | |
const promiseObj = () => new Promise((resolve, reject) => { | |
// generate a random 2 digit positive integer | |
const randomNum = Math.floor(Math.random() * 100) | |
if (randomNum % 2 === 0) { | |
resolve(randomNum + " is even") | |
} | |
else { | |
reject(randomNum + " Promise is rejected, putin") | |
} | |
}) | |
async function main() { | |
console.log("Start"); | |
try { | |
const res = await promiseObj() | |
console.log(res, "Promise is resolved"); | |
} catch (error) { | |
console.error(error); | |
} | |
console.log("end of program"); | |
} | |
main() |
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