CC-06: String Mutations

with Carmen Salas • 2024/10/10

slides

• Strings

• Concatenation

• Carmen's Code Snippets

• Code Challenge

Strings

Strings are made up of chars. Every char in a string has a corresponding position index, allowing direct access to them. As a result, strings are iterable, and indices start at 0

Some string properties/methods:

• .length returns the size of the string

• .toUpperCase() and .toLowerCase() works for both char and string. This is because char in JavaScript is also a string.

Concatenation

Various ways to add strings

Although what JS really does is just make a new resulting string, since strings are immutable.

• using the +/+= operator (can be between a str<->str, str<->num, etc.)

• using String methods like .concat(), .padEnd(), .repeat()

Carmen's Code Snippets

//Review of strings
/*
- Strings are made up of characters.

- Every character in a string has a position, this position is called the index. You can access any charcater in a string if you know it's position

- This means that strings are iterable. 
- Zero based indices 

Some string properties/methods:
- "hello".length  === 5
   01234
   Bracket notation: "hello"[2] //"l"
- .toUpperCase() / .toLowerCase()

Concatenation:
"hello" + "o" -> "helloo"

*/
let str = "hello";

for (let i = 0; i <= str.length - 1; i++) {
  console.log(i);
  console.log(typeof str[i]);
}

// let empty = "";
// empty += "h";
// console.log(empty);
// empty += "i";
// console.log(empty);

Code Challenge

1. Declare a function named reverseString that takes in a string argument and returns the reversed version of the string, without using any .reverse() JavaScript methods. Hint: How can you use a loop iterate through a string backwards?

const reverseString = (str) => {
  res = "";

  for (let i = str.length-1; i >= 0; i--) {
    res += str[i];
  }

  return res
}

// console.log(reverseString("hello"))  //"olleh"
// console.log(reverseString("oo"))     //"oo"
// console.log(reverseString(""))       //""

1. Declare a function named reverseZigZagString that takes in a string argument and returns the reversed version of the string with characters alternating in uppercase and lowercase, without using any .reverse() JavaScript methods.

const reverseZigZagString = (str) => {
  // setup:
  // `res` to build up
  // `small` to alternate properly when string length is even
  res = "";
  let small = true;
  for (let i = str.length-1; i >= 0; i--) {
    // account for spaces
    if (str[i] == ' ') {
      res += str[i];
      continue;
    }
    // alternate chars
    (small) ? res += str[i].toLowerCase() : res += str[i].toUpperCase();
    small = !small;
  }

  return res;
}

// console.log(reverseZigZagString("hello")) //"oOlLeH"
// console.log(reverseZigZagString("Fellows"))    //"sWoLlEf"
// console.log(reverseZigZagString("Code Challenge"))  //"eGnElLaHc EdOc"