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)](https://stackoverflow.com/questions/6660977/convert-hyphens-to-camel-case-camelcase) — Sangwin Gawande, Jun 15 '17 at 04:06

Pointy · Accepted Answer · 2016-02-03T21:03:59.797

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 03 '16 at 21:03

answered Oct 12 '11 at 16:51

Pointy

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2

That gives `listSI`. You need `+ newArr[i].substr(1)` – lonesomeday Oct 12 '11 at 16:52
If iterating array from 1, expression won't get applied when it's only single element in array. Loop should have `var i = 0`. – Teo Dragovic Aug 21 '16 at 09:27
@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". – Pointy Aug 21 '16 at 13:12
do you need to use charAt or could you skip this step? – coder123 Jul 15 '19 at 21:37
1

@coder123 you could use `newArr[i][0].toUpperCase()` if you prefer. – Pointy Jul 15 '19 at 22:37
@Pointy doesn't work that way, because the strings in JavaScript are immutable, See https://stackoverflow.com/a/4717855/10851804 – NAND Aug 07 '20 at 08:49
@NAND yes I know, see the end of the answer – Pointy Aug 07 '20 at 12:08

score 9 · Answer 2 · edited Sep 06 '19 at 20:54

9

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

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

edited Sep 06 '19 at 20:54

MrCorote

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answered Jul 11 '18 at 19:40

Mostafa Elhusseiny

91
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2

2

You should consider adding some explanation, as well as properly formatting the code you posted. – norok2 Jul 11 '18 at 20:03

score 7 · Answer 3 · answered Dec 29 '17 at 21:03

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

score 6 · Answer 4 · answered Oct 12 '11 at 16:52

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 '11 at 16:52

RoccoC5

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score 3 · Answer 5 · answered Dec 17 '18 at 21:37

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 '18 at 21:37

afxentios

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score 3 · Answer 6 · answered Dec 31 '21 at 20:48

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"]

score 2 · Answer 7 · answered Jan 21 '16 at 12:54

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");

score 2 · Answer 8 · edited May 17 '18 at 11:15

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);
}

score 2 · Answer 9 · answered Oct 12 '11 at 16:58

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
*/

score 2 · Answer 10 · answered Oct 12 '11 at 16:59

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 '11 at 16:59

Vivek Viswanathan

1,968
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score 1 · Answer 11 · answered Aug 28 '19 at 08:54

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);

score 1 · Answer 12 · answered Jan 16 '20 at 06:42

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 '20 at 06:42

Masum Billah

2,209
21
20

score 0 · Answer 13 · answered Jun 15 '17 at 03:50

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.

score 0 · Answer 14 · answered Dec 02 '19 at 13:29

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;
}

score 0 · Answer 15 · answered Apr 17 '21 at 17:05

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);
}

score 0 · Answer 16 · answered Feb 10 '22 at 19:10

0

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 '22 at 19:10

Kayra Berk Tuncer

185
2
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Trying to capitalize the first character in array of strings, why this is not working?

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