#day1 Javascript Variable

#Day1 #BackToBasics
1) const and Let Keywords are introduced in Es6 2015.

2) LET : LET has a Block Scope
VAR : VAR has a Function Scope

Let: it signals that variable can be assigned reassigned a different value
(it means let can be reassigned).
eg:- let meal = 'Enchiladas';
console.log(meal); // Output: Enchiladas
meal = 'Burrito';
console.log(meal); // Output: Burrito

3) if we don't assign a value to a variable it will give an output of undefined.

4) Const: const was introduced in es6 it is constant. if you try to redefine const variable it will give you TypeError: Assignment to constant variable.

5) constant variables need to assign a value at the time of declaration and if you don't assign a value it will give you SyntaxError.

6) Mathematical Operators
7) +=,
8) -=
9) *=
10) /=

11) String Interpolation : it can be done with `` this BackTics.
eg:- const myPet = 'armadillo';
console.log(`I own a pet ${myPet}.`);

12) Typeof operator: return the typeof variables (string, num, etc...)


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.

Apply your learning with Projects based on Javascript Variables.do it now

1) Kelvin Project
2) Dog Years

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