Variables

• Variable hold reusable data in a program and associate it with a name. Variables are stored in memory.
• ‘var‘ keyword is used in pre-ES6 versions of JS
• ‘let‘ is the preferred way to declare a variable. It can be reassigned.
• ‘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.
• + 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.