Difference between var, let, and const in Javascript
var
, let
, and const
are three ways to declare variables in JavaScript. Here is a brief overview of each:
var
: Variables declaredvar
have function scope, meaning they are accessible within the function they are declared in. If a variable is declaredvar
outside of a function, it has a global scope and can be accessed anywhere in the code.var
declarations are hoisted, which means they are moved to the top of their scope and can be used before they are declared.let
: Variables declaredlet
have block scope, meaning they are only accessible within the block they are declared in. This makeslet
a better choice for local variables within loops or other control structures.let
declarations are also hoisted but cannot be accessed before they are declared.const
: Variables declared withconst
have block scope, just likelet
. The critical difference is thatconst
variables cannot be reassigned after they are displayed. This makesconst
a good choice for declaring values that should not change, such as constant mathematical values or configuration settings.
In general, it is recommended to use const
by default and only use let
when you need to reassign the value of a variable. var
should be used sparingly, as the behavior of function scope and hoisting can lead to unexpected results.
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