How to check if a string character is in a JavaScript array?

Question

I'm trying to make a JavaScript function that tells how many times a vowel was repeated in a given string.

Here's what I have tried:

 function checkVowel(str) {
 vowels = ['a', 'e', 'i', 'o', 'u']
 str = "hello world"
 
 for(let i = 0; i < str.length; i++){
 if(str[i].includes(vowels)){
 console.log("worked")
 } else {
 console.log("not worked")
 }
 }
}
checkVowel()

How can I make this function check for each vowel rather than the entire array at once?

• ggorlen: str[i].includes(vowels) => vowels.includes(str[i]). You might also want to remove the hardcoded str = "hello world"--call the function with checkVowel("hello world") instead, so you can reuse the function for different strings.
• Thomas: Do you want to count the number of occurrences for each vowel, or how many vowels there are in total in that string?
• Roarke: The first one actually.

Answer 1

Is it this what you're looking for?

function checkVowel(str) {
 const counts = Object.seal({ a: 0, e: 0, i: 0, o: 0, u: 0 });
 
 for (let char of str) {
 counts[char.toLowerCase()]++;
 }
 
 return counts;
}
console.log(checkVowel("hello world"));

• DecPK: Perfect combination of seal and for of loop. Learned something new.
• DecPK: But it fails if any charater is in upper case
• Roarke: Now, I have been trying to display the number of times a vowel was repeated using string template literal but it's not working. Can you help me with that?
• Thomas: @IshaanSharma Same game. Make a new question (don't mix multiple/different questions in one post), show what you've tried, what you got and what you expected. Even with my answer and your comment above, there's a dozen ways that you could have written this and a hundred things that could have gone wrong.
• Roarke: Got it! Thought duplicates post aren't allowed.

Answer 2

Another solution

function countVowel(word) {
 const vowels = ["a", "e", "i", "o", "u"];
 const wordArray = word.split("").map((s) => s.toLowerCase());
 const result = {
 a: 0,
 e: 0,
 i: 0,
 o: 0,
 u: 0
 };
 return wordArray.reduce((acc, curr) => {
 if (vowels.includes(curr)) {
 ++acc[curr];
 }
 return acc;
 }, result);
}
console.log(countVowel("Angel"));

• Thomas: What's your intention? Downwards compatibility? And since you already have it: curr in result is quicker O(1) than vowels.includes(curr) O(n)