Return longest string in array (JavaScript) [duplicate]

Question

So I'm trying to find the longest string in an array of strings. I've done a problem similar to this before where I had to return the length of the longest string. The thing is, my code works and returns 11 when it looks like this:

var long1= 0;

var plorp = ["bbllkw", "oox", "ejjuyyy", "plmiis", "xxxzgpsssa", "xxwwkktt", "znnnnfqknaz", "qqquuhii", "dvvvwz"];

function longestString(arr){
  for (i=0; i<arr.length; i++){
      if (arr[i].length > long1){
        long1= arr[i].length;
      }

  }
  return long1;
}

but, if I change long1= arr[i].length; to long1 = arr[i]; it just returns arr[0] instead. Am I missing something here? The loop seems to be iterating correctly otherwise.

Edit: that is to say, it returns bbllkw.

You are overriding an integer value with a string and trying to use one variable for multiple things. You should keep long1= arr[i].length and return arr[long1] at the end. — user3151675
– user3151675, Commented Sep 8, 2017 at 23:41
@the4akman you are incorrect. long1 contains longest length not index. So arr[long1] will very likely be undefined. — Zamrony P. Juhara
– Zamrony P. Juhara, Commented Sep 8, 2017 at 23:55

Dekel · Accepted Answer · 2017-09-09 00:17:37Z

14

You can use reduce instead:

var plorp = ["bbllkw", "oox", "ejjuyyy", "plmiis", "xxxzgpsssa", "xxwwkktt", "znnnnfqknaz", "qqquuhii", "dvvvwz"];
var longest = plorp.reduce(function(a, b) { 
  return a.length > b.length ? a : b
}, '');
console.log(longest);

Or ES6 version:

var plorp = ["bbllkw", "oox", "ejjuyyy", "plmiis", "xxxzgpsssa", "xxwwkktt", "znnnnfqknaz", "qqquuhii", "dvvvwz"];
var longest = plorp.reduce((a, b) => a.length > b.length ? a : b, '');
console.log(longest);

edited Sep 9, 2017 at 0:17

answered Sep 8, 2017 at 23:39

Dekel

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3 Comments

Andy Over a year ago

Nice concise ES6 1-liner too: plorp.reduce((p, c) => p.length > c.length ? p : c).

Dekel Over a year ago

@Andy Thanks for the reply. I was thinking about writing this as ES6 but wasn't sure the OP can use ES6 in his env.... Added this to the answer as well. Thanks!

leandraaar Over a year ago

This is great! I'm a bit new to ES6, but it makes sense. Also, I'm a girl :)

user8012147 · Accepted Answer · 2017-09-08 23:45:32Z

3

Simply you must change long declaration to :

var long1= '';

and in the for loop condition it should be

arr[i].length > long1.length

answered Sep 8, 2017 at 23:45

user8012147

Comments

C.Unbay · Accepted Answer · 2018-03-13 20:27:31Z

3

Updated after a user wanted more basic solution

In here we find the longest length of an array item with reduce function, and then filter the array with the elements which have that length with filter function. It returns us multiple elements if they have the same but longest length

var plorp = ['sameLength', 'someoth', 'asfzc', 'sameLLngth'];
    ln = plorp.reduce((r,s) => r > s.length ? r : s.length, 0);


const result = plorp.filter(pl => pl.length == ln);

console.log(result);

Old Answer

If there are more than one longest string in the array, it will return an array of them. If there is only one longest, it will return the string, and not an array.

var plorp = ["bbllkw", "oox", "ejjuyyy", "plmiis", "xxxzgpsssa", "xxwwkktt", "znnnnfqknaz", "qqquuhii", "dvvvwz"];
var wholeArr = [];

function longestString(arr) {
    var tlength = 0;
    for(var i =0; i < plorp.length; i++){
      if(tlength < plorp[i].length){
        tlength = plorp[i].length;
      }
    }
    for(var j =0; j < plorp.length; j++){
      if(plorp[j].length == tlength){
         wholeArr.push(plorp[j]);
      }
    }
   if(wholeArr.length == 1){
     return wholeArr[0]
   }else{
      return wholeArr
  }
}


console.log(longestString(plorp));

edited Mar 13, 2018 at 20:27

answered Sep 8, 2017 at 23:53

C.Unbay

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3 Comments

Gismo Ranas Over a year ago

excellent, but is there a way to write it more functional and not so verbose?

C.Unbay Over a year ago

Yes, I have updated it for you @GismoRanas

Gismo Ranas Over a year ago

I ended up finding my own solution and I wrote it below. Thanks!

Bharti Ladumor · Accepted Answer · 2017-09-09 06:44:58Z

1

var arr = ["first", "second", "third", "fourth", "thousand"]

function getLongestString(arr) { let longestStringArr = arr.sort((a, b) => a.length - b.length).reverse(); return longestStringArr[0]; }

console.log(getLongestString(arr))

answered Sep 9, 2017 at 6:44

Bharti Ladumor

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Comments

user4447799 · Accepted Answer · 2017-09-08 23:43:02Z

0

Just compare the length of the strings and then assign the string itself to long1.

var plorp = ["bbllkw", "oox", "ejjuyyy", "plmiis", "xxxzgpsssa", "xxwwkktt", "znnnnfqknaz", "qqquuhii", "dvvvwz"];

function longestString(arr) {
  var long1 = arr[0];
  for (i = 0; i < arr.length; i++) {
    if (arr[i].length > long1.length) {
      long1 = arr[i];
    }
  }
  return long1;
}


console.log(longestString(plorp));

answered Sep 8, 2017 at 23:43

user4447799

Comments

Zamrony P. Juhara · Accepted Answer · 2017-09-09 00:13:26Z

0

The problem is when you set

long1=arr[i];

And you compare with length which is integer value.

At first iteration, you compare integer value of 0 with length of first string which of course make the comparison expression result true and you set

 long1=arr[0];

For next iteration, long1 no longer contain integer value but string so comparison between length and long1 always return false.

That is why you always get first string as result.

You need to initialize long1 as empty string and use long1.length for comparison as suggested by belhadj's answer.

edited Sep 9, 2017 at 0:13

answered Sep 9, 2017 at 0:05

Zamrony P. Juhara

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Comments

slevy1 · Accepted Answer · 2017-09-10 00:26:20Z

0

Another solution involves the array's sort method and a comparison function, but that can be a "heavy" solution as per MDN:

Depending on the compareFunction's nature, this may yield a high overhead. The more work a compareFunction does and the more elements there are to sort, the wiser it may be to consider using a map for sorting.

So, taking the preceding advice, here's one way to obtain the longest string using a map in conjunction with an array's sort method, as follows:

var plorp = ["bbllkw", "oox", "ejjuyyy", "plmiis",
             "xxxzgpsssa", "xxwwkktt", "znnnnfqknaz",
             "qqquuhii", "dvvvwz"];

function getLongestStr() {
  var mapped = plorp.map((el, i) => ({ index: i, length: el }) );
  mapped.sort((a, b) => {

      if (a.length > b.length) {
        return -1;
      }
   
      if (a.length < b.length) {
        return 1;
      }
      return 0;
  });

// DESC order so longest string in 0th element
  return mapped.map((el) => plorp[el.index])[0];
}
console.log( getLongestStr() );

Interesting related discussion here.

edited Sep 10, 2017 at 0:26

answered Sep 9, 2017 at 0:22

slevy1

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1 Comment

Scott Sauyet Over a year ago

Using a sort just to find the max is very heavyweight. See instead the answer from @Dekel, which is probably as clean as it's going to get.

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