Summary  
This chapter explains how var declarations can be redeclared and are hoisted—leading to undefined when printing before their declaration—whereas let (and const) disallow redeclaration and are not hoisted.

General domain of usage  
Web development

## 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:

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)


### 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;

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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The syntax of the JavaScript programming language is the set of rules that defines how a JavaScript program will be written and interpreted (by both the runtime system and by human readers).

JavaScript is dynamically typed (also called loosely typed) scripting language. That is, in javascript variables can receive different data types over time. Datatypes are basically typed of data that can be used and manipulated in a program.

Var 2/3

Var Tolerate Redeclaration

解答

Variable hoisting