为什么我必须将我的字符串推入数组中才能再次将其重新加入？

Question

So I want to capitalize the starting letter of each word in a string. Here's how I did it:

function LetterCapitalize(str) { 
var arr = str.split(" ");
var newArr = [];
  for(i = 0; i < arr.length; i++) {
    var newStr = arr[i].toString();
    newArr.push(newStr.substring(0,1).toUpperCase() + newStr.substring(1,newStr.length));
  }
  return newArr.join(" ");

}

This code is correct and the first letter of every word in the string was capitalized. However, when I tried to shorten my code like this, it only returned the last word of the string with the first letter capitalized, but nothing else:

function LetterCapitalize(str) { 
var arr = str.split(" ");
var newArr = [];
  for(i = 0; i < arr.length; i++) {
    var newStr = arr[i].toString();
  }
  return newStr.substring(0,1).toUpperCase() + newStr.substring(1,newStr.length);

}

Basically, what I did was remove the part where I push the new string into a new array, only to join it back into a string.

Answer 1

Problem is in the for loop part code. Here in every iteration the newstr get the value of arr[i].toString(); and the old value ie arr[i-1].toString(); which is in newStr is overwritten. Hence only the last iteration value is stored in newStr

for(i = 0; i < arr.length; i++) {
 var newStr = arr[i].toString();
}

Try this:

 function LetterCapitalize(str) { var arr = str.split(" "); var newStr = ""; for(i = 0; i < arr.length; i++) { var temp = arr[i].toString(); newStr = newStr + temp.substring(0,1).toUpperCase() + temp.substring(1,temp.length)+" "; } return newStr; } alert(LetterCapitalize("hello i am rohit ")); 

Answer 2

Perhaps you got confused by the return in the MAP functionality:

 function LetterCapitalize(str) { var arr = str.split(" "), newArr = arr.map( function(word) { return word.substring(0,1).toUpperCase() + word.substring(1); }); return newArr.join(" "); } alert(LetterCapitalize("This is a test")) 

Answer 3

You may achieve this through replace function without splitting.

function LetterCapitalize(str) { 
  return str.replace(/(^| )([a-z])/g, function(x,y,z) {
    return y+z.toUpperCase()
  }
    )
}
console.log(LetterCapitalize('foo bar buz'))