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I'm trying to do a check that the first array contains the same values of the second array. However I'm confused about my code.

First question is: why is my code running my else statement if all letters in the first array are contained in the second? it will run 2 lines of "this is not valid"

Second question is: if my first array contains a duplicate letter it will still pass the check e.g ["a", "b" , "a", "d", "e", "f"]; even though there is two a's in the first it will see the same "a" again. Anyone know a way around this.

Sorry for my long winded questions but I hope it makes sense. Thanks :)

var letters = ["a", "b" , "c", "d", "e", "f"];
var otherLetters = ["a","b", "c" , "d", "e", "f"];

var i = -1;

while(i<=letters.length){



i++;
    if(otherLetters.includes(letters[i])){
        console.log("This is valid");
    }

    else 

    console.log("This is not valid");



}
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7 Answers 7

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1

You didn't close the brackets. And your loop is very confusing, please use foreach. Here is a working example:

const letters = ["a", "b" , "c", "d", "e", "f"];
const otherLetters = ["a","b", "c" , "d", "e", "f"];

letters.forEach(el => {
  if (otherLetters.includes(el)) {
    console.log(el + 'is valid');
  } else {
    console.log(el + 'is not valid');
  }
});
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1 Comment

Thanks Nico, I feel quite silly now haha. Thanks for your answer was able to fix up my code :)
1

You are trying to access array elements which are out of bounds. The script runs 8 iterations over an array with 6 elements.

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1 Comment

Thanks Matthias, got it sorted now :)
0

Nothing to worry, cpog90.

Try this solution.

    var letters = ["a", "b" , "c", "d", "e", "f"];
    var otherLetters = ["a","b", "c" , "d", "e", "f"];
    
    var i = 0;
    while(i<letters.length){
        if(otherLetters.includes(letters[i])){
            console.log("This is valid");
        }
        else {
           console.log("This is not valid "+i);
        }
        i++;
    }

What went wrong in your logic?

If you declare i = -1 and while(i<=letters.length), As 6 is length of letters, 8 iterations will be done as follows.

For first iteration (i = -1), 'while' condition returns true and checks for 'a'

output: This is valid

For second iteration (i = 0), 'while' condition returns true and checks for 'b'

output: This is valid

For third iteration (i = 1), 'while' condition returns true and checks for 'c'

output: This is valid

For fourth iteration (i = 2), 'while' condition returns true and checks for 'd'

output: This is valid

For fifth iteration (i = 3), 'while' condition returns true and checks for 'e'

output: This is valid

For sixth iteration (i = 4), 'while' condition returns true and checks for 'f'

output: This is valid

For seventh iteration (i = 5), 'while' condition returns true and checks for undefined value.

output: This is not valid

For eighth iteration (i = 6), 'while' condition returns true and checks for undefined value.

output: This is not valid

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1 Comment

Thanks for the clear explanation What If! Again I dunno why I thought I would start from -1 lol. Was able to fix my code up :)
0

First of all you have set i = -1 which is confusing since array start position is 0. The reason your loop is running two extra times is because loop started at -1 instead of 0 and next the condition i <= length.

Since [array length = last index + 1] your loop runs extra two times. Just to make your code work assign var i = 0 and while condition i < letters.length

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Comments

0

Simplest solution is using lodash. It has all optimizations out-of-the-box:

var letters = ["a", "b" , "c", "d", "e", "f"];
var otherLetters = ["f", "a","b", "c" , "d", "e"];

const finalLetters = _.sortBy(letters);
const finalOtherLetters = _.sortBy(otherLetters);

if (_.isEqual(finalLetters, finalOtherLetters)) {
  console.log('Two arrays are equal.');
} else {
  console.log('Two arrays are not equal.');
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

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0

Arrays are index based and starts from 0. So, the -1 and the less than letters.length check puts the code into out of bounds.

var letters = ["a", "b" , "c", "d", "e", "f"];
var otherLetters = ["a","b", "c" , "d", "e", "f"];
var i = 0;
while(i<letters.length)
{
    if(otherLetters.includes(letters[i]))
    {
        console.log("This is valid");
    }
    else
    {
        console.log("This is not valid");
    }
    i++;
}
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1 Comment

Thanks Abhishek! I have no idea why i decided to start from -1 tbh. I think my brain is fried lol.
0

You can use a combination of Array.prototype.every with Array.prototype.includes, along with some extra guard clauses.

const areSequenceEqual = (arr1, arr2) => {
  if (!arr1 || !arr2) {
    return false;
  }

  if (arr1.length !== arr2.length) {
    return false;
  }

  return arr1.every(x => arr2.includes(x));
};

const letters = ["a", "b", "c", "d", "e", "f"];
const otherLetters = ["a", "b", "c", "d", "e", "f"];
const someOtherLetters = ["a", "b", "c", "d", "e", "f", "g"];

console.log(areSequenceEqual(letters, otherLetters));
console.log(areSequenceEqual(letters, undefined));
console.log(areSequenceEqual(letters, someOtherLetters));

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1 Comment

Thanks Kunal, I was able to make use of the include method to resolve my issue :)

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