JavaScript Variables

4 Ways to Declare a JavaScript Variable:

• Using var
• Using let
• Using const
• Using nothing  

  What are Variables?

  Variables are containers for storing data (storing data values).

  In this example, x, y, and z, are variables, declared with the var keyword:  

  Redeclaring a Variable Using let 

  Redeclaring a variable inside a block will not redeclare the variable outside the block:

•  Redeclaring a variable using the let keyword can solve this problem.

  When to use JavaScript const?

  Always declare a variable with const when you know that the value should not be changed.

  Use const when you declare:

  • A new Array
  • A new Object
  • A new Function
  • A new RegExp  

    Constant Objects and Arrays

    The keyword const is a little misleading.

    It does not define a constant value. It defines a constant reference to a value.

    Because of this you can NOT:

    • Reassign a constant value
    • Reassign a constant array
    • Reassign a constant object

    But you CAN:

    • Change the elements of constant array
    • Change the properties of constant object

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    Constant Arrays

    You can change the elements of a constant array: