reading-notes

JavaScript Functions

Reading

• Functions - Reusable Blocks of Code

Notes

Functions

• Allow you to store pieces of code for reuse throughout your program
• Hallmark sign is () at the end of a word
• Must be declared with function
• Must be invoked to run with ()
• Can take arguments/parameters inside the (), or may have optional parameters

Anonymous Functions

• Functions with no name
• Typically take another function as an argument
• keydown event & logKey example
  • Instead of defining a separate logKey function to record keystrokes, you can just pass the function directly into another function like so:

  // Declaring a Separate Function
  function logKey(event) {
  console.log(`You pressed "${event.key}".`);
  }
  
  textBox.addEventListener('keydown', logKey);
  
  // Passing the function directly with Anonymous Function
  textBox.addEventListener('keydown', function(event) {
  console.log(`You pressed "${event.key}".`);
  });
  

  • You can also use Fat Arrow Notation to create the function without having to write function

  textBox.addEventListener('keydown', (event) => {
  console.log(`You pressed "${event.key}".`);
  });