Review Variables

 VARIABLES

Review Variables

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.
• 
  

This part is just for review and understanding please revise it ok.

let catName = 'Minnie';
let catAge = 5;

let sentence = 'My cat is called ' + catName + ' , and is ' + catAge + ' years old.';

console.log(typeof sentence);

Instructions:

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.

Solution:

1.console.log(test1);

var test1 = 'hahaha'

Terminal:

Nobins-MacBook-Pro:STOC_MODULE 11SEPT 2022 nobinpunyo$ node test.js

undefined

2.console.log(test1);

let test1 = 'hahaha'

Terminal:

ReferenceError: Cannot access 'test1' before initialization

3.console.log(test1);

const test1 = 'hahaha'

Terminal:

SyntaxError: Unexpected identifier