4.3 - "Strings"

Something Cool

  • Code editors have become very smart. They make our lives so much easier with tons of helpful shortcuts, autocomplete, and more.

  • Replit is no exception. Take a look at all the things you can do in a code window, just by pressing F1 (search + 1 on a Chromebook).
    Notable helpful shortcuts include:

      • Toggling comments (line or block)

      • Indent / outdent

      • Move a line up or down

      • Delete all left/right

      • Change all occurrences

      • Format document

      • Go to bracket

      • Insert line above


  • for-loops help us to enumerate through values (count and loop in a sequential order)

let answer = 0;

// Add 1+2+3+4+5+6+7+8+9+10

for (let index = 1; index <= 10; index++) {

answer += index;


console.log(answer); // 55

  • A byte of data is a number, written in binary. Computers only know numbers. So how do we see letters?

Mr. Squirrel's Joke of the Day

"Today I learned that if you turn a canoe over, you can wear it as a hat.

Because it's capsized!"

Today's Lesson: 4.3 - "Strings"

  • A single letter is called a character (char).

  • Each character is a symbol (drawing) with a number behind it. The computer looks-up the symbol, based on the number.

  • Many characters together is called a String of characters.

    • For Example: The word hello is a string made of the chars 'h' 'e' 'l' 'l' 'o'.

    • A char is primitive. They're very boring. Not much we can do with them.

    • A String is an object. Lots of neat properties and functions available to them.

    • Note: JavaScript treats single letters as a String, not a char.

Properties and Functions

It is very important to remember that "a" and "A" are considered different. At no point is the string "Hello" equal to "hello".

A property is a fact about that object or thing.

Strings have a very important property - length

let myString = "Hello World!";

console.log(myString.length); // Prints 12 to the screen

A function - also known as a method - is something that an object can do or give or utilize to manipulate data or give a result.
Strings have lots of useful functions but the ones we will focus on are:

  • charAt()

  • charCodeAt()

  • toUpperCase() and toLowerCase()

  • substring() and substr()

  • replace()

  • and many more, with awesome examples at w3schools!

Extracting & Changing Characters

  • There is a shortcut to the charAt() method for finding a char at a specific location:

    • Square brackets with a location (index): "Hello World"[6] will return 'W'

let text = "My name is Mr. Squirrel";
log(text.length); // 23
log(text[1]); // y
log(text[23]); // undefined

  • Now that we know for-loops, we can loop through a string!

let longText = "Supercalifragilisticexpialidocious";

for (let letter = 0; letter < longText.length; letter++) {



  • Strings are immutable. This means you cannot modify a single character without destroying and recreating the memory space.
    let text = "My name is Mr. Squirrel";
    text[3] = "Z" // This does nothing

4.3 Task(s) / Homework