Trying to capitalize the first character in array of strings, why this is not working?

Question

I'm trying to write a function that converts for example list-style-image to listStyleImage.

I came up with a function but it seems not working. Can anybody point me to the problem here ?

var myStr = "list-style-image";

function camelize(str){
    var newStr = "";    
    var newArr = [];
    if(str.indexOf("-") != -1){
        newArr = str.split("-");
        for(var i = 1 ; i < newArr.length ; i++){
            newArr[i].charAt(0).toUpperCase();
        }       
        newStr = newArr.join("");
    }
    return newStr;
}

console.log(camelize(myStr));

Possible duplicate of Convert hyphens to camel case (camelCase) — Sangwin Gawande
– Sangwin Gawande, Commented Jun 15, 2017 at 4:06
This seems to be a classical example of an xy problem: The OP actually wants to convert a kebab case string to a lower camel case string but they ask about how to capitalize strings in an array... — Kai Roesner
– Kai Roesner, Commented Dec 6, 2024 at 14:58

Pointy · Accepted Answer · 2016-02-03 21:03:59Z

22

You have to actually re-assign the array element:

    for(var i = 1 ; i < newArr.length ; i++){
        newArr[i] = newArr[i].charAt(0).toUpperCase();
    }

The "toUpperCase()" function returns the new string but does not modify the original.

You might want to check to make sure that newArr[i] is the empty string first, in case you get an input string with two consecutive dashes.

edit — noted SO contributor @lonesomeday correctly points out that you also need to glue the rest of each string back on:

         newArr[i] = newArr[i].charAt(0).toUpperCase() + newArr[i].substr(1);

edited Feb 3, 2016 at 21:03

answered Oct 12, 2011 at 16:51

Pointy

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7 Comments

lonesomeday Over a year ago

That gives listSI. You need + newArr[i].substr(1)

Teo Dragovic Over a year ago

If iterating array from 1, expression won't get applied when it's only single element in array. Loop should have var i = 0.

Pointy Over a year ago

@TeoDragovic the original question wanted to skip the first character; in other words, a single character value like "a" should result in the same string, "a".

coder123 Over a year ago

do you need to use charAt or could you skip this step?

Pointy Over a year ago

@coder123 you could use newArr[i][0].toUpperCase() if you prefer.

|

MrCorote · Accepted Answer · 2019-09-06 20:54:49Z

9

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

days.map( a => a.charAt(0).toUpperCase() + a.substr(1) );

edited Sep 6, 2019 at 20:54

MrCorote

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answered Jul 11, 2018 at 19:40

Mostafa Elhusseiny

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1 Comment

norok2 Over a year ago

You should consider adding some explanation, as well as properly formatting the code you posted.

martinkzn · Accepted Answer · 2017-12-29 21:03:56Z

7

Here is my solution with ES6. This is an example where I store the days of the week in my array and I uppercase them with for... of loop.

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

for (let day of days) {
    day = day.charAt(0).toUpperCase() + day.substr(1);
    console.log(day);
}

Here is a link to the documentation: for... of loop documentation

answered Dec 29, 2017 at 21:03

martinkzn

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Comments

RoccoC5 · Accepted Answer · 2011-10-12 16:52:32Z

6

In your for loop, you need to replace the value of newArr[i] instead of simply evaluating it:

for(var i = 1 ; i < newArr.length ; i++){
    newArr[i] = newArr[i].charAt(0).toUpperCase() + newArr[i].substr(1);
}

answered Oct 12, 2011 at 16:52

RoccoC5

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Comments

afxentios · Accepted Answer · 2018-12-17 21:37:39Z

3

Since JavaScript ES6 you can achieve the "camelization" of an array of strings with a single line:

let newArrCamel= newArr.map(item=> item.charAt(0).toUpperCase() + item.substr(1).toLowerCase())

answered Dec 17, 2018 at 21:37

afxentios

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Comments

Dae-mon · Accepted Answer · 2021-12-31 20:48:30Z

3

Here is my solution using the slice() method.

const names = ["alice", "bob", "charlie", "danielle"]

const capitalized = names.map((name) => {
    return name[0].toUpperCase() + name.slice(1)

})

console.log(capitalized)

// Expected output: // ["Alice", "Bob", "Charlie", "Danielle"]

answered Dec 31, 2021 at 20:48

Dae-mon

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Comments

kennebec · Accepted Answer · 2011-10-12 16:58:37Z

2

You don't need the array to replace a hyphen and a lowercase letter with the uppercase-

function camelCase(s){
    var rx=  /\-([a-z])/g;
    if(s=== s.toUpperCase()) s= s.toLowerCase();
    return s.replace(rx, function(a, b){
        return b.toUpperCase();
    });
}

camelCase("list-style-image")

/*  returned value: (String)
listStyleImage
*/

answered Oct 12, 2011 at 16:58

kennebec

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Comments

Vivek Viswanathan · Accepted Answer · 2011-10-12 16:59:44Z

2

you need to store the capitalized letter back in the array. Please refer the modified loop below,

for(var i = 1 ; i < newArr.length ; i++)
{
    newArr[i] = newArr[i].charAt(0).toUpperCase() + newArr[i].substr(1,newArr[i].length-1);
}

answered Oct 12, 2011 at 16:59

Vivek Viswanathan

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Comments

Jmorazano · Accepted Answer · 2016-01-21 12:54:06Z

2

A little bit longer but it gets the job done basically playing with arrays:

function titleCase(str) {
  var arr = [];
  var arr2 = [];
  var strLower = "";
  var strLower2 = "";
  var i;
  arr = str.split(' ');

  for (i=0; i < arr.length; i++) {

    arr[i] = arr[i].toLowerCase();
    strLower = arr[i];
    arr2 = strLower.split('');
    arr2[0] = arr2[0].toUpperCase();
    strLower2 = arr2.join('');
    arr[i] = strLower2;
  }

  str = arr.join(' ');

  return str;
}

titleCase("I'm a little tea pot");

answered Jan 21, 2016 at 12:54

Jmorazano

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Comments

IKavanagh · Accepted Answer · 2018-05-17 11:15:30Z

2

The substr() method returns the part of a string between the start index and a number of characters after it. Source: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];
for (let day of days) {
  day = day.substr(0, 1).toUpperCase() + day.substr(1);
  console.log(day);
}

edited May 17, 2018 at 11:15

IKavanagh

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answered May 17, 2018 at 10:55

Julius Omwanza

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Comments

kaleem · Accepted Answer · 2019-08-28 08:54:11Z

1

Here's another solution though I am so late in the game.

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

let capitalize = days.map(day => day.charAt(0).toUpperCase() + day.slice(1).toLowerCase());

console.log(capitalize);

answered Aug 28, 2019 at 8:54

kaleem

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Comments

Masum Billah · Accepted Answer · 2020-01-16 06:42:40Z

1

Let's checkout the code below.

['sun','mon'].reduce((a,e)=> { a.push(e.charAt(0).toUpperCase()+e.substr(1)); return a; },[]);

Output: ["Sun", "Mon"]

answered Jan 16, 2020 at 6:42

Masum Billah

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Comments

Kayra Berk Tuncer · Accepted Answer · 2022-02-10 19:10:26Z

1

my best way is:

function camelCase(arr) {
  let calc = arr.map(e => e.charAt(0).toUpperCase() + e.slice(1)).join('')
  console.log(calc)
  return calc;
}

// Test
camelCase(['Test', 'Case'])

answered Feb 10, 2022 at 19:10

Kayra Berk Tuncer

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Comments

Pre Vizsla · Accepted Answer · 2017-06-15 03:50:24Z

0

function titleCase(str){    // my codelooks like Jmorazano but i only use 4 var.
var array1 = [];
var array2 = []; 
var array3 = "";
var i;
array1 = str.split(" ");
for (i=0; i < array1.length; i++) {
array1[i]= array1[i].toLowerCase();
array2=array1[i].split("");
array2[0]=array2[0].toUpperCase();
array3 = array2.join("");
array1[i] = array3;}

str = array1.join(' ');
return str;}
titleCase("I AM WhO i aM"); //Output:I Am Who I Am
// my 1st post.

answered Jun 15, 2017 at 3:50

Pre Vizsla

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Comments

Roninho · Accepted Answer · 2019-12-02 13:29:40Z

0

Here is how I would go about it.

function capitalizeFirst(arr) {
  if (arr.length === 1) {
    return [arr[0].toUpperCase()];
  }
  let newArr = [];
  for (let val of arr) {
    let value = val.split("");
    let newVal = [value[0].toUpperCase(), ...value.slice(1)];
    newArr.push(newVal.join(""));
  }
  return newArr;
}

answered Dec 2, 2019 at 13:29

Roninho

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Comments

Abdu Wahed Nur · Accepted Answer · 2021-04-17 17:05:19Z

0

Please check this code below

 var months = ['january', 'february', 'march', 'april', 'may', 'june', 'july', 'august', 'september', 'november', 'decembar'];

for(let month of months){
    month = month.charAt(0).toUpperCase() + month.substr(1);
    console.log(month);
}

answered Apr 17, 2021 at 17:05

Abdu Wahed Nur

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Comments

M K Saifullah Mollick · Accepted Answer · 2024-12-02 16:46:37Z

0

const names = ['bob', 'marry', 'alice', 'jenifer']; const capitalized = names.map((name) => { return( name[0].charAt(0).toUpperCase() + name.slice(1) + ' ' ) }); console.log(capitalized)

answered Dec 2, 2024 at 16:46

M K Saifullah Mollick

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1 Comment

Community Dec 3, 2024 at 20:55

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.

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