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JavaScript: Change the characters (lower case) in a string where a turns into z, b turns into y, c turns into x, ..., n turns into m, m turns into n, ..., z turns into a

JavaScript Basic: Exercise-134 with Solution

Write a JavaScript program to change the characters (lower case) in a string where a turns into z, b turns into y, c turns into x, ..., n turns into m, m turns into n, ..., z turns into a.

Pictorial Presentation:

JavaScript: Change the characters (lower case) in a string where a turns into z, b turns into y, c turns into x, ..., n turns into m, m turns into n, ..., z turns into a.

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>Change the characters (lower case) in a string where a turns into z, b turns into y, c turns into x, ..., n turns into m, m turns into n, ..., z turns into a</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function change_char(str1) {
	var result = [];
	for (var i = 0; i < str1.length; i++)
    {
		var char_order = str1.charCodeAt(i) - 'a'.charCodeAt(0),
			change_char = 25 - char_order + 'a'.charCodeAt(0);
		result.push(String.fromCharCode(change_char));
	}
	return result.join("");
}
console.log(change_char("abcxyz"));
console.log(change_char("python"));

Sample Output:

zyxcba
kbgslm

Flowchart:

Flowchart: JavaScript - Change the characters (lower case) in a string where a turns into z, b turns into y, c turns into x, ..., n turns into m, m turns into n, ..., z turns into a

ES6 Version:

function change_char(str1) {
	const result = [];
	for (let i = 0; i < str1.length; i++)
    {
        const char_order = str1.charCodeAt(i) - 'a'.charCodeAt(0);
        const change_char = 25 - char_order + 'a'.charCodeAt(0);
        result.push(String.fromCharCode(change_char));
    }
	return result.join("");
}
console.log(change_char("abcxyz"));
console.log(change_char("python"));

Live Demo:

See the Pen javascript-basic-exercise-134 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