LetterChanges – JavaScript

Question

First trial didn't work because string is immutable.

function LetterChanges(str) { 
  // want c->d & z->a; a,e,i,o,u capitalized
  for(i=str.length-1;i>=0;i--){
    if(str[i]=="c"){str[i]="d"}
    if(str[i]=="z"){str[i]="a"}
    if(str[i]=="a"||"e"||"i"||"o"||"u"){str[i]=str[i].toUpperCase()}
  }
  return str;          
}

LetterChanges("I love you, Catz") // should return "AtAD ,UOy EvOl I"

Second trial: WHY DOES IT CAPITALIZE EVERYTHING? It should capitalize vowels only.

function LetterChanges(str) { 
  var changed = ""
  // c->d & z->a; a,e,i,o,u capitalized
  for(i=str.length-1;i>=0;i--){
    if(str[i]=="c"){changed+="d"}
    else if (str[i]=="C"){changed+="D"}
    else if(str[i]=="z"){changed+="a"}
    else if(str[i]=="Z"){changed+="A"}
    else if(str[i]=="a"||"e"||"i"||"o"||"u"){changed+=str[i].toUpperCase()}
    else {changed+=str[i]}
  }
  return changed; 
}
LetterChanges("CapuoZ") // should return "AOUpAD" but instead it returns "AOUPAD", capitalizing non-vowels.

I want the function LetterChanges to change letter c to d & z to a and capitalize a, e, i, o u. The code above wouldn't change anything for some reason. i.e., the changes are not saved. — user3164317, Apr 30 '15 at 21:10

score 1 · Accepted Answer · answered Apr 30 '15 at 21:13

1

String objects are immutable, which means you can't directly change their values. I'm sure there are better ways you can do it, but one simple way is to just create a second variable and keep adding to it as you go along.

answered Apr 30 '15 at 21:13

Dalannar

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1
2
11

Thanks, Dalannar. can you please take a look at my second trial? – user3164317 Apr 30 '15 at 21:26

score 0 · Answer 2 · answered Apr 30 '15 at 21:25

function LetterChanges(str) { 
    var newStr = str.replace("c", "d").replace("z", "a")
        .replace("a", "A").replace("e", "E").replace("I", "i")
        .replace("o", "O").replace("u", "U");  
    return newStr;          
}

A better way to do it would be to store all the transformations in an array or list (like "c" -> "d") and then iterate over them

Rolo · Answer 3 · 2015-04-30T21:37:20.710

@Dalannar is right you can't directly change the values, here is the fiddle with your example working:

Your original post didn't unclude the upper case A and Z, here is the updated example: http://fiddle.jshell.net/rvxe8nq5/2/

  function LetterChanges(str) { 
  // want c->d & z->a; a,e,i,o,u capitalized
  var result = "";
  for(i=str.length-1;i>=0;i--){
    switch(str[i]) {
        case "c":
            result += "d";
            break;
        case "C":
            result += "D";
            break;
        case "z":
            result += "a";
            break;
        case "Z":
            result += "A";
            break;
        case "a":
        case "e":
        case "i":
        case "o":
        case "u":
            result += str[i].toUpperCase();
            break;
        default:
            result += str[i];
    }    
  }
  return result;          
}

alert(LetterChanges("I love you, Catz"));

score 0 · Answer 4 · edited May 23 '17 at 10:24

It is possible to do such operation in JS. The problem is as @Dalannar mansion, there isn't build-in option to set character at index. The following link contains replaceAt function witch implemented in JS:

How do I replace a character at a particular index in JavaScript?

(Copy the replaceAt function code)

Now you can modify character at index:

str = str.replaceAt(i, 'some string here');

And the last change is to make else-if condition

function LetterChanges(str) {
    for(var i=str.length-1;i>=0;i--){
        if (str[i] == 'c') {
            str = str.replaceAt(i, 'd');
        } else if (str[i] == 'z') {
            str = str.replaceAt(i, 'a');
        } else if(['a', 'e', 'i', 'o', 'u'].indexOf(str[i]) != -1) {
            str=str.replaceAt(i, str[i].toUpperCase());
        }
    }
    return str;          
}

LetterChanges("I love you ccc"); // I lOvE yOU ddd

LetterChanges – JavaScript

4 Answers4