Higher Order Functions with callback function and array

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1

Hello, I am trying to practice Higher Order Functions and Iterators and my code keeps returning undefined and I can’t figure out what I’m doing wrong.

const persons121 = [
‘Oliver’, ‘Lorenzo’, ‘Micaela’, ‘Rosario’, ‘Clara’
];

const namesWithVowel = (array121) => {
let result = array121.forEach(name => {
return name[0] === ‘O’;
});
console.log(result);
}

let doesBeginWithVowel = function(func, array) {
let check = func(array);
console.log(In the list ${check} is the name that begins with a vowel);
}

doesBeginWithVowel(namesWithVowel, persons121);

// my code returns the following:

In the list undefined is the name that begins with a vowel

I would be very grateful if someone can help me out. I apologize if I have missed something obvious. Many thanks.

2

What is the first thing we learned about, Array.forEach()?

3

Yes you’re right, it returns undefined… but even so if I use a different iterator it also returns undefined.

4

Then we need to rethink the problem. The lower part of your code invokes a higher order function that takes two arguments. A function, and an array of string data. What is it meant to return? An array of strings that begin with a vowel. One of the iterators we learned about is aptly suited to this task; which is it?

1 Like
5

I think it is .map() — but that also returns undefined… i must be missing something

6

.map() can be used as a conditional iterator, but it returns an array the same size as the original. You’re getting warmer.

1 Like
7

I am back with forEach()… unless I use findIndex() to locate the index and then log the word with the matching index.

8

Now you’re getting colder.

10

filter() — returns an array containing the matching results.

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11

If I call the namesWithVowel(persons121) then it logs [‘Oliver’]

So that function is working…

However when I call the higher order functon:

doesBeginWithVowel(namesWithVowel, array121)

then I get undefined… so the problem must be here

12

I figured it out… thank you for pointing me in the right direction.

Here is the code that works:

const persons121 = [
‘Oliver’, ‘Olivia’, ‘Lorenzo’, ‘Micaela’, ‘Rosario’, ‘Clara’
];

const namesWithVowel = (array121) => {
let result = array121.filter(name => {
return name[0] === ‘O’;

});       
 return result.join(", ");

}

let doesBeginWithVowel = (funct, array543) => {
console.log(The names ${funct(array543)} in the list begin with vowels);

};

doesBeginWithVowel(namesWithVowel, persons121);

// it returns — The names Oliver, Olivia in the list begin with vowels

1 Like