Overview
In JavaScript, variables are used to store data that will be used in multiple places. This allows the data to be kept in one place for ease of change.
Variables can be declared using three different methods: var, let, and const. See the JavaScript resource on var vs. let vs. const to see how and when each should be used.
var
“var” is typically used when a value may change over time. But since 2015, var is not often used in favor of using “let”.
var x = 5;let
“let” is typically used when a value is restricted to the block { } of code where it is created.
- Variables declared with let have Block Scope
- Variables declared with let must be Declared before use
- Variables declared with let cannot be Redeclared in the same scope
let x = 5;const
“const” is typically used when a value CANNOT change over time.
- Variables declared with const have Block Scope
- Variables declared with const must be Declared before use
- Variables declared with const cannot be Redeclared or Reassigned
const first_name = 'Johnny';JavaScript Notes:
- When using JavaScript, single or double quotation marks are acceptable and work identically to one another; choose whichever you prefer, and stay consistent
- JavaScript is a case-sensitive language; firstName is NOT the same as firstname
- JavaScript variables are case sensitive (x is not the same as X)
- Arrays count starting from zero NOT one; so item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on
- JavaScript variables must begin with a letter, $, or _
We’d like to acknowledge that we learned a great deal of our coding from W3Schools and TutorialsPoint, borrowing heavily from their teaching process and excellent code examples. We highly recommend both sites to deepen your experience, and further your coding journey. We’re just hitting the basics here at 1SMARTchicken.