Variable Scope Confusion 😵

Question

if i have a function like this:

function myFunc(a, b) {
return a+b;
}

My question is, Variable a, b is local or global?

function myFunc2() {
c=8;
d=1;
return c+d;
}

what about c and d?

Answer 1

KrOW, sorry.
i have edited the question what about now?

Thanks Serena Yvonne and KrOW
i understood now 🤗

Answer 2

Serena Yvonne
You are right in that undeclared variable is global, the reason is that they will be added as a property to window. See Morpheus demo below for detailed explanation.

https://code.sololearn.com/WwhKQUoMbXHH/?ref=app

Nevertheless, it's not a good habit to use variable without declaration.

Answer 3

Scope works differently if you use var/let/const or nothing. If you declare a variable withouth using keyword, it will be in global scope without taking cure where you declared it.

function f1(){
function inner(){
imGlobal= true
}
inner();
}

f1();
console.log(imGlobal);//true

If you use var, you var will have like scope the entire encosling function if its declared inside a function, or global if its not.

function f2(){
// Note this block dont prevent imLocal to be
// putted inside f2 scope
{
var imLocal= 'local';
}
function inner(){
imLocal= 'local-inner';
}
inner();
console.log(imLocal); //local-inner
}
f2();

If you use let keyword, then your var will be block-scoped (or global if its declared outside any block). Repeating same example for var but using let, you will have:
- imLocal in inner will create a global var
- log imLocal inside f2 function will print imLocal (than in reality is global) declared by inner function because the imLocal inside f2 is not visible anymore because its block-sopec (remember the block)

function f2(){
// Note this block prevent imLocal to be
// putted inside f2 scope NOW respect var example
{
let imLocal= 'local';
}
function inner(){
imLocal= 'local-inner';
}
inner();
console.log(imLocal); //local-inner
}
f2();

Using const is similar to let but it dont allow redefinitions of variable in same scope

Answer 4

a and b are locals to function myFunc.
The second function is not even executable because it raise a parsing error (var in arguments)

Answer 5

A lot has already been said, however I suggest you read my blog post on variable declarations in javascript to get more insight.

https://code.sololearn.com/WdauYjg8rOiF/?ref=app

Hope it helps, happy coding!

Answer 6

In general, scope is area between a pair of curly braces. Variables belong to the scope in which they are declared. Btw KrOW has answered your question.

Answer 7

a and b are local to the function myFunc, and the value of a+b is returned.
a and b are the parameters of myFunc, or place holder for the values you pass to myFunc.

In myFunc2 , c and d are global to it, they must be defined in an outter block of code. myFunc2 changes c to 8 and d to 1 for the whole world. Oh, myFunc2 always returns 9.

In javascript undeclared variables default to program wide globals.

Answer 8

A and B is local to myfunc

And c and d are global for myfunc and vice versa

Answer 9

all the variables are local, because they are described and declared inside the functions

Answer 10

return statement must bring them back to the to the main scope. am i right?

Answer 11

The variables a and b are local to the function MyFunc.and also c and d are local variables to the function myFunc2.(NOTE:In the second function declare the variable with datatypes.).

Answer 12

local

Answer 13

a global var is created outside of function, it will be accessible anywhere in doc. and a local var which created in fun. , it will work only in that function

Answer 14

In order to declare a global variable, you must declare it outside all functions. All variables declared inside of a function's opening and closing braces arocal variables to that function.

Answer 15

All the variables a local as they are declared inside a function

Answer 16

Hi