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JavaScript: Create a new array taking the first and last elements from a given array of integers and length must be greater or equal to 1

JavaScript Basic: Exercise-76 with Solution

Write a JavaScript program to create a new array taking the first and last elements from a given array of integers and length must be greater or equal to 1.

Pictorial Presentation:

JavaScript: Create a new array taking the first and last elements from a given array of integers and length must be greater or equal to 1.

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JavaScript program to create a new array taking the first and last elements from a given array of integers and length must be greater or equal to 1.</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function started(nums) {
     var array1 = [];
     array1.push(nums[0], nums[nums.length - 1]);

     return array1;
}
console.log(started([20, 20, 30]));
console.log(started([5, 2, 7, 8]));
console.log(started([17, 12, 34, 78]));

Sample Output:

[20,30]
[5,8]
[17,78]

Flowchart:

Flowchart: JavaScript - Create a new array taking the first and last elements from a given array of integers and length must be greater or equal to 1

ES6 Version:

function started(nums) {
     const array1 = [];
     array1.push(nums[0], nums[nums.length - 1]);

     return array1;
}
console.log(started([20, 20, 30]));
console.log(started([5, 2, 7, 8]));
console.log(started([17, 12, 34, 78]));

Live Demo:

See the Pen JavaScript - Create a new array taking the middle elements of the two arrays of integer and each length 3 - basic-ex-75 by w3resource (@w3resource) on CodePen.


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Next: Write a JavaScript program to test if an array of integers of length 2 contains 1 or a 3.

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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