scope - mutation inside a function in javascript -

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n00b question here:

suppose call function updates number or string this

var x = "well"; var helloify = function(str){   str += "hello" };

i'd expect behavior:

helloify(x); console.log(x) \\ "well hello"

but instead get

\\ "well"

doesn't "+=" change value of "x"? change persist in scope of function not in global environment?

thanks!

--confused

when call helloify(x); pass value of x (a string) not reference x.

str += "hello" modifies str , leaves x alone.

nb: objects addressed reference, if x had been reference object have modified single object addressed both variables. simple strings not objects though.


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