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

问题

I'm a beginner at Javascript. 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));

回答1:

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);

回答2:

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);
}

回答3:

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

回答4:

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
*/

回答5:

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);
}

回答6:

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");

回答7:

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);
}

回答8:

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())

回答9:

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

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

回答10:

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.

回答11:

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);

来源：https://stackoverflow.com/questions/7743582/trying-to-capitalize-the-first-character-in-array-of-strings-why-this-is-not-wo