Clash Royale CLAN TAG#URR8PPP

Make a function in javascript that returns the array and elements in reverse order

As I said in the title, I want to make a function that receives an array and return all the elements in reverse order. I studied a lit bit of javascript, but this is bugging me for some time. I made two functions to make it clear, as even my friends didn't understand the concept, the second is the one who is bugging me.

const reverse = (pal) =>
var aux = "";
for(var i in pal)
aux = pal[i] + aux;

return aux;

console.log(reverse("are")); //=> returns "era"

This function above works fine and returns only one word, the next needs to return the array and all the words in reverse (just in case if someone didn't understand)

const reverPal = (pal) =>
let aux = "";
let aux1 = "";
for (var i in pal)
aux += pal[i]
for (var i in aux.length) //I think the problem starts here
aux.forEach((word) =>
word.reverse();
aux1 += word;
)


return aux1;


console.log(reverPal(["hello", "how", "are", "you"]));
//should return = "olleh", "woh", "era", "ouy"
//but returns nothing in this code

Can someone help me?

console.log()

debugger;

5 Answers
5

You could always just use the reverse() function. This function will do the following:

reverse()

hi

['h', 'i']

['h', 'i']

['i', 'h']

['i', 'h']

ih

const reverPal = (pal) =>
return pal.map(word => word.split('').reverse().join(''));


console.log(reverPal(["hello", "how", "are", "you"]));

An easy, functional, way to reverse a string is to spread it into an array and call reverse() on it and the join() it back up:

reverse()

join()

let word = "hello"

console.log([...word].reverse().join(''))

You can apply this to each element of your array with map():

map()

reverPal = (arr) => arr.map(word => [...word].reverse().join(''))

console.log(reverPal(["hello", "how", "are", "you"]))

You're not making an array in your second function

const reverPal = (pal) =>
let aux = "";
let aux1 = "";
for (var i in pal)
aux += pal[i]
for (var i in aux.length) //I think the problem starts here
aux.forEach((word) =>
word.reverse();
aux1 += word;
)


return aux1;
//console.log(reverPal(["hello", "how", "are", "you"]);
//should return = "olleh", "woh", "era", "ouy"
//but returns nothing in this code


You want reverPal to return an array but where are you creating the array?

reverPal

It seems like you want to just use your first function in your second

const reverse = (pal) =>
var aux = "";
for(var i in pal)
aux = pal[i] + aux;

return aux;


const reverPal = (pal) =>
let aux1 = ;
for (var i in pal)
aux1.push(reverse(pal[i]));

return aux1;
;
console.log(reverPal(["hello", "how", "are", "you"]));
//should return = "olleh", "woh", "era", "ouy"
//but returns nothing in this code

Or if you wanted to not use the first in the second then just paste the first inside the second

const reverPal = (pal) =>
let aux1 = ;
for (var i in pal)
var pal1 = pal[i];
var aux = "";
for(var i in pal1)
aux = pal1[i] + aux;

aux1.push(aux);

return aux1;
;
console.log(reverPal(["hello", "how", "are", "you"]));
//should return = "olleh", "woh", "era", "ouy"
//but returns nothing in this code

All that said there's a few things you should probably get to know about JavaScript

Don't use for(elem in array) in JavaScript.

for(elem in array)

see: Why is using "for...in" with array iteration a bad idea?

Consider never using var ever

var

Now that const and let both exist there is never a reason to use
var. var has a host of issues that both const and let solve.

const

let

var

var

const

let

See: https://hackernoon.com/why-you-shouldnt-use-var-anymore-f109a58b9b70

If you're just looking for a solution rather than your actual question of "making a function" others have posted more idiomatic solutions.

I want to make a function that receives an array and return all the elements in reverse order.

If you want reverse array element order:

function reverseArr(arr)
var outArr = ;
for (var i = arr.length-1;i>=0;i--)
outArr.push(arr[i]);

return outArr;

console.log(reverseArr([1,2,3]));
// [3, 2, 1]


If you want reverse characters in a string:

function reverseString(s)
var outS = "";
for (var i = s.length-1;i>=0;i--)
outS += s[i];

return outS;

console.log(reverseString("abc中"));
// 中cba


Since you already have a working function that outputs a reversed word, you can just pass that function into Array.map.

const reverse = (pal) =>
var aux = "";
for(var i in pal)
aux = pal[i] + aux;

return aux;


const reverPal = (arr) =>
return arr.map(reverse);


console.log(reverse("hello"));
console.log(reverPal(["hello", "how", "are", "you"]));
//should return = "olleh", "woh", "era", "ouy"

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