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variables.js
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variables.js
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// 'use strict';
/*
Homework Assignment #2: Variables and Constants
1st paragraph - hoisting
2nd paragraph - var
3rd paragraph - let
4th paragraph - const
After each paragraph follows a code example
*/
/*
HOISTING
- works with var variables only
- a variable can be used before it's declared in
code - JavaScript by default moves all var
variables to top before execution
- does not work with let and const
- declared and initialized var variables are not
hoisted
- declarations are hoisted to the top of their
scope
- if a variable is used before declaration in the
strict mode an error is raised
*/
// EXAMPLE 1:
bookName = 'Book1';
console.log(bookName);
var bookName;
// EXAMPLE 2:
bookName = 'Book1';
console.log(bookName);
let bookName;
// EXAMPLE 3:
bookName = 'Book1';
console.log(bookName);
const bookName;
// EXAMPLE 4:
console.log(bookName);
var bookName = 'Book1';
// EXAMPLE 5:
'use strict'
bookName = 'Book1';
console.log(bookName);
var bookName;
/*
VAR
- declares a variable with global scope
- value can be multiple-times overwritten
- it's visible in nested block(s) of block,
in which isthe var variable declared
- in case variable is called outside of a block,
in which it's declared it return its last
assigned value
- outside of this nested block (where was a new
value assigned) can program see the
variable with a new value
EXAMPLE:
*/
if (true) {
var bookName = 'Book1';
if (true) {
bookName = 'Book2';
console.log(bookName);
}
console.log(bookName);
}
console.log(bookName);
/*
LET
- declares a variable with local (block) scope
- value can be multiple times overwritten
- it's visible in nested block(s) of block,
in which is the let variable declared
- in case variable is called outside of a block,
in which it's declared an error is raised
- outside of this nested block (where was a new
value assigned) can program see the
variable with a new value
EXAMPLE:
*/
if (true) {
let bookName = 'Book1';
if (true) {
bookName = 'Book2';
console.log(bookName);
}
console.log(bookName);
}
console.log(bookName);
/*
CONST
- declares a variable with local (block) scope
- value can be assigned just once
- assigning a new value doesn't rise error, but
execution stops
- it's visible in nested block(s) of block,
in which is the const variable declared
- in case variable is called outside of a block,
in which it's declared an error is raised
- outside of this nested block (where was a new
value assigned) can program see the
variable with a new value
EXAMPLE:
*/
if (true) {
const bookName = 'Book1';
if (true) {
// bookName = 'Book2';
console.log(bookName);
}
console.log(bookName);
}
console.log(bookName);