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Introduction to JavaScript

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Var 2/3

Var Tolerate Redeclaration

Var tolerates the redeclaration. If a variable is declared with the same name twice with var we will not get an error, but with let we will get an error. For instance:

let user = 'Mike';
let user = 'John';

              
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let user = 'Mike';
let user = 'John';
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But we can declare variables with the same names with var and the old values of the variables are simply overwritten, for example.

var user = 'Mike';
var user = 'John';
console.log(user)

              
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var user = 'Mike';
var user = 'John';
console.log(user)
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Завдання

Swipe to start coding

Declare a variable company and assign the value " Apple". Redeclare the company and now set the value “Samsung” by using the var keyword. Show the updated value on the console.

Рішення

var company="Apple";
var company="Samsung";
console.log(company);

Variable hoisting

Hoisting, in JavaScript, is a way where a function or a variable can be used before its declaration.
In JavaScript, var is hoisted while the let and const does not allow hoisting, for example.

totalNumber = 10;
console.log(totalNumber);
var totalNumber;

              
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totalNumber = 10;
console.log(totalNumber);
var totalNumber;
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If we use the variable inside console.log() and nothing is written before it we will get an undefined value. In JavaScript first, the memory is allocated to the variable and initially, their values are undefined after this they are assigned some values.

console.log(company)
var company="panasonic";

              
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console.log(company)
var company="panasonic";
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