Ebook – JavaScript

The Modern Javascript

• Types
  • Use “null” to write an “empty” or an “unknown” value into the variable
  • “undefined” is only used for checks, to see if the variable is assigned or not
    • The meaning of undefined is “value is not assigned”
    • If a variable is declared, but not assigned, then its value is exactly undefined
• Functions
  • Callback functions
  • Function Declaration and Function Expression
  • Arrow Functions

    [js]let sum = (a, b) => a + b;
    alert( sum(1, 2) ); // 3[/js]

    This equals to

    [js]let sum = function(a, b) {
    return a + b;
    };[/js]

    • Multiline Arrow Functions

      [js]let sum = (a, b) => { // the figure bracket opens a multiline function
      let result = a + b;
      return result; // if we use figure brackets, must use return
      };

      alert( sum(1, 2) ); // 3

      [/js]