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JavaScript: Count the number of vowels in a given string

JavaScript Basic: Exercise-54 with Solution

Write a JavaScript program to count the number of vowels in a given string.

Pictorial Presentation:

JavaScript: Count the number of vowels of a given string

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JavaScript program to count the number of vowels in a given string.</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function vowel_Count(str)
{ 

  return str.replace(/[^aeiou]/g, "").length; 
}

console.log(vowel_Count("Python"));
console.log(vowel_Count("w3resource.com"));

Sample Output:

1
5

Flowchart:

Flowchart: JavaScript - Count the number of vowels in a given string

ES6 Version:

function vowel_Count(str)
{ 

  return str.replace(/[^aeiou]/g, "").length; 
}

console.log(vowel_Count("Python"));
console.log(vowel_Count("w3resource.com"));

Live Demo:

See the Pen JavaScript - count the number of vowels in a given string - basic-ex-54 by w3resource (@w3resource) on CodePen.


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Previous: Write a JavaScript program to check if the characters a and b are separated by exactly 3 places anywhere (at least once) in a given string.
Next: Write a JavaScript program to check if a given string contains equal number of p's and t's present.

What is the difficulty level of this exercise?



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