Nice work! This lesson introduced you to variables, a powerful concept you will use in all your future programming endeavors.

Let’s review what we learned:

  • Variables hold reusable data in a program and associate it with a name.
  • Variables are stored in memory.
  • The var keyword is used in pre-ES6 versions of JS.
  • let is the preferred way to declare a variable when it can be reassigned, and const is the preferred way to declare a variable with a constant value.
  • Variables that have not been initialized 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 is used to concatenate strings including string values 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.


To learn more about variables take on these challenges!

  • Create variables and manipulate the values.
  • Check what happens when you try concatenating strings using variables of different data types.
  • Interpolate multiple variables into a string.
  • See what happens when you use console.log() on variables declared by different keywords (const, let, var) before they’re defined. For example:
console.log(test1); const test1 = 'figuring out quirks';
  • Find the data type of a variable’s value using the typeof keyword on a variable.
  • Use typeof to find the data type of the resulting value when you concatenate variables containing two different data types.

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