 # JavaScript: Find the smallest prime number strictly greater than a given number

## JavaScript Basic: Exercise-129 with Solution

Write a JavaScript program to find the smallest prime number strictly greater than a given number.

Pictorial Presentation: Sample Solution:

HTML Code:

``````<!DOCTYPE html>
<html>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title> Find the smallest prime number strictly greater than a given number</title>
<body>

</body>
</html>
```
```

JavaScript Code:

``````function next_Prime_num(num) {
for (var i = num + 1;; i++) {
var isPrime = true;
for (var d = 2; d * d <= i; d++) {
if (i % d === 0) {
isPrime = false;
break;
}
}
if (isPrime) {
return i;
}
}
}

console.log(next_Prime_num(3));
console.log(next_Prime_num(17));
``````

Sample Output:

```5
19
```

Flowchart: ES6 Version:

``````function next_Prime_num(num) {
for (let i = num + 1;; i++) {
let isPrime = true;
for (let d = 2; d * d <= i; d++) {
if (i % d === 0) {
isPrime = false;
break;
}
}
if (isPrime) {
return i;
}
}
}

console.log(next_Prime_num(3));
console.log(next_Prime_num(17));
``````

Live Demo:

See the Pen javascript-basic-exercise-129 by w3resource (@w3resource) on CodePen.

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﻿

## JavaScript: Tips of the Day

Promise object

```const myPromise = () => Promise.resolve('I have resolved!');

function firstFunction() {
myPromise().then(res => console.log(res));
console.log('second');
}

async function secondFunction() {
console.log(await myPromise());
console.log('second');
}

firstFunction();
secondFunction();
```

With a promise, we basically say I want to execute this function, but I'll put it aside for now while it's running since this might take a while. Only when a certain value is resolved (or rejected), and when the call stack is empty, I want to use this value.
We can get this value with both .then and the await keyword in an async function. Although we can get a promise's value with both .then and await, they work a bit differently.
In the firstFunction, we (sort of) put the myPromise function aside while it was running, but continued running the other code, which is console.log('second') in this case. Then, the function resolved with the string I have resolved, which then got logged after it saw that the callstack was empty.
With the await keyword in secondFunction, we literally pause the execution of an async function until the value has been resolved before moving to the next line.
This means that it waited for the myPromise to resolve with the value I have resolved, and only once that happened, we moved to the next line: second got logged.

Ref: https://bit.ly/3jFRBje