Swap Case on JavaScript

Swap Case on javascript

Like Ian said, you need to build a new string.

var swapCase = function(letters){
    var newLetters = "";
    for(var i = 0; i<letters.length; i++){
        if(letters[i] === letters[i].toLowerCase()){
            newLetters += letters[i].toUpperCase();
        }else {
            newLetters += letters[i].toLowerCase();
        }
    }
    console.log(newLetters);
    return newLetters;
}

var text = 'So, today we have REALLY good day';

var swappedText = swapCase(text); // "sO, TODAY WE HAVE really GOOD DAY"

Swap Cases- switch from lowercase to uppercase and viceversa

There are multiple issues with this code,

1. The array should not run to length, so it should be < instead of <=

2. There is no need for 3 loops

3. result.join should join with an empty string instead of blank space

4. Intendations are all over the place.

see corrected code below:

function SwapCase(str) { 
  let cap=str.toUpperCase()
  let low=str.toLowerCase()
  let arr=str.split("")  
  let result=[]

  for(var i=0; i<arr.length;i++){  
    if(arr[i]===cap[i]){ 
      result.push(arr[i].toLowerCase())
    } 
    if(arr[i]===low[i]){ 
      result.push(arr[i].toUpperCase())
    }
  } 
  return result.join("")
}

console.log(SwapCase("heLLo"))

Swapcase Javascript

Your code has a few errors:

1. JavaScript is case-sensitive: is the function called swapcase or swapCase?
2. string isn't a great variable name, especially because you refer to it by a different name (letters) at the end of the function.
3. Your comparison operators are inverted. Try >= 'a', <= 'z', etc.
4. JavaScript is case-sensitive: you should be calling toUpperCase and toLowerCase.
5. You're never calling swapCase aside from inside the function itself.

The fixed version:

var swapCase = function(str) {
    var letters = str.split("");
    for (var i = 0; i < letters.length; i++) {
        if (str.charAt(i) >= 'a' && str.charAt(i) <= 'z') {
            letters[i] = str.charAt(i).toUpperCase();
        } else if (str.charAt(i) >= 'A' && str.charAt(i) <= 'Z') {
            letters[i] = str.charAt(i).toLowerCase();
        }
    }
    str = letters.join("");
    console.log(str);
    return str;
};

var text = "Life is 10% what happens to you, and 90% of how you REACT to it";
swapCase(text);

An easier way to test the case of a character would be:

if (str.charAt(i).toLowerCase() === str.charAt(i)) {
    // Character is lower case or not a letter
} else {
    // Character is upper case
}

More efficient JS case swap

It sounds like: for every character, I want to make it Upper if it's Lower, and Lower if it's Upper.

That's very easy:

function swapCase(str) {
  var out = '';
  for (var i=0; i<str.length; i++) {
    // It's lower, or non-A-Z
    if (str[i].toLowerCase() == str[i]) {
      out += str[i].toUpperCase();
    }
    else {
      out += str[i].toLowerCase();
    }
  }
  return out;
}

alert(swapCase('Hello World Sup Bro My Name iS Richard!'));

(And the Fiddle to prove it.](http://jsfiddle.net/rudiedirkx/m4mhsyuz/)

How to change every character to opposite case in Javascript?

Strings are immutable, they don't change when using methods like toLowerCase(), they return a new string that is changed, and you have to assign that new string to something :

function changeCase() {
    var str = document.getElementById("changeCase").innerHTML,
        str2 = '';

    for (var i = 0; i < str.length; i++) {
        if (str.charAt(i) === str.charAt(i).toLowerCase()) {
            str2 += str.charAt(i).toUpperCase();
        } else if (str.charAt(i) === str.charAt(i).toUpperCase()) {
            str2 += str.charAt(i).toLowerCase()
        } else {
            str2 += str.charAt(i);
        }
    }
    console.log(str2, "after");
}

FIDDLE

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