Scoping in JavaScript
Scoping - Definition, Type , Lifetime
1 November, 2022
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Scope refers to the availability/accessibility of variables.
For illustrating , suppose we have two scopes thar are given below.
In general, if a variable defined inside
your scope , you can’t access it outside their scope. But your scope can access elements defined outside of it i.e in their scopeMainly 3 types of scopes exists in JavaScript:
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Block Scope
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Function Scope
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Global Scope
Block Scope
Above example will throw an error
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You can access outside scope element from inside scope but reverse is not true.
But if we use
var keyword to create that scope than above example will not throw any errorLocal Scope
If we use declare a variable inside a function in JavaScript , then the variable created has a local scope. Also any parameters defined in function protoype are also Local.
Function Scope:
Variables declared inside a function are not accessible from outside the function.
Global Scope:
Variables created in this scope can be accessed anywhere inside the script.
Do it yourself with
var & const global variables and try to access them inside the function.If you don’t declare variable with any keyword(const,let,var) but initialize them with a value, they will be automatically declared as a global variable.
But in case of functions you also need to call the function to make it work
All modern browsers support running JavaScript in
Strict Mode. So I will not suggest you to use undecalred variables, otherwise you have to debug.But I highly suggest you to not use any global variable. Because anyone can change its values and it will be harder for us to debug.
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The lifetime of a JavaScript variable starts when it is declared.
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Function (local) variables are deleted when the function is completed.
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In a web browser, global variables are deleted when you close the browser window (or tab).
Comment if I have committed any mistake.
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