Variables

A variable is a “named storage” for values or data

• Use real-life analogy of a named ingredients in a kitchen
• JavaScript application needs to work with information. E.g Catalogue list holding shopping items, Chat application holding messages, names etc
• Create a variable using the let and const keyword. We’ll take about their difference later.
• Can declare multiple variables in single line separated by comma
• Talk about var and its availability in older script. Discourage it’s usage

Variables (Naming conventions)

• The name must contain only letters, digits, or the symbols $ and _ . Required
• The first character must not be a digit. Required
• Use camelCase when variables contain multiple words Optional
• Case matters: Variables named apple and AppLE are two different variables.
• Reserved Names/Keyword cannot be used. E.g let let = 5; let return = 5; 

Variables (const)

• Variables declared with const do not change and cannot be re-assigned
• It is a convention in JS to CAPITALIZE const variable names
• Separate multiple words with under_score

Variables (let)

• Variables declared with let can change and be re-assigned
• Variable names should be descriptive and it’s intention should be clear
• It is recommended to use camelCase for long variables
• A variable name should have a clean, and meaning obvious.
• Variable naming is one of the most important and complex skills in programming.
• Some good-to-follow rules are:
  • Use human-readable names like userName or shoppingCart.
  • Rarely use abbreviations or short names like a, b, c
  • Make names maximally descriptive and concise. Examples of bad names are data and value..
  • Agree on terms within your team and in your own mind. If a site visitor is called a “user” then we should name related variables currentUser or newUser instead of currentVisitor or newManInTown.