<aside> 💡 Reviewing Javascript

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Introduction to Javascript

Review of lesson

• Data is printed, or logged, to the console with console.log

  • Console: A panel that displays messages

  console.log("message")
  

  • Either a variable or a single string can be printed in the console

• Comments:

  • Single-line comments: [//comment](//comment)
  • Multi-line comments: /* comment in between */

• 7 fundamental data types in JavaScript:

  • Strings
    • Characters wrapped in single or double quotes: 'Sample String"
  • Numbers
    • Any number without quotes: 23.8879, 18
  • Booleans
  • Null
  • Undefined
  • Symbol
  • Object
    • Including instances of data types, objects can have properties, or stored information.
    • The properties are denoted with . after the name of the object: 'Helo'.length
    • Objects can have methods which perform actions: 'hello'.toUpperCase()
    • Built-in objects, including Math are collections of methods and properties that JavaScript provides VV

• The built-in arithmetic operators include + - * / %

Variables - Review

• Variables hold re-usable data in a program and associate it with a name
• Variables are stored in memory
• The var keyword is used in pre-ES6 version of JavaScript
• let is the preferred way to declare a variable when it can be reassigned
  • const is used for variables that should not and therefore cannot be reassigned
• Variables that have not been initialized with a value store the primitive data type undefined
• Mathematical assignment operators make it easy to calculate a new value and assign it to the same variable.
• The + operator can be used to concatenate strings, including string variables held in variables
• In ES6, template literals use backticks ``` and ${} to interpolate values into a string.
• The typeof keyword returns the data type (as a string) of a value.