Can someone explain this to me i have no idea what str and " number" do here and how they function


#1


so capitalize has (str) in it … i have no idea what that is… str is short for string
but in order for that to be a string it needs " "
but this is just (str) . i have no idea what its purpose is there since it doesn’t actually say that its a str ,theres no var str = ""
that defines that short term for a string so im really confused what its doing there.

I understand for example var city =“paris” thats a string
i somewhat understand that when you put var capital = capitalize(city), im guessing it wants function capitalize and var city
to change the var city that is, they want it to have the first letter capitalized . but what purpose does the (str) at the begining have to do with it… couldnt that capitalize() be empty and still work?

And this!!! This blows my mind , what in gods name does "number " mean here … correct me if i’m wrong but even though it says number if its in " " it makes it a string . in my eyes str === “number” . str isnt a string and “number” isnt a number. does the "number " mean something in js ? bcs to me THAT looks like a string .


#2

this examples assume you have a console where you can see the output, if you don’t, use jsbin, console.log() will log the output to the console

i think first and for most its important to understand function parameter concept, lets create a function with parameter x:

// function with parameter x
function example(x){
    console.log(x)
}

// function calls with arguments for parameter
example("hello world")
example("parameters vs arguments")

see comments in code, the arguments at function get passed into the function parameter (x), so now x contains a string, if you like you can think that JS does this under the hood when function is called with argument "hello world":

x="hello world"

now i hope you understand why str contains a string ("paris")

typeof is a built in function that returns a string with the data of str

we can see this:

function capitalize(str){
    console.log(typeof str)
}

capitalize("paris")
capitalize(37)

see how typeof returns the data type as string? So if we check for a certain data type, we can just check if typeof str equals a certain datatype

37 is of data type number, so typeof returns "number" which allows us to check if 37 is a number


#3

w8 so is “number” also built in function ?


#4

no, number is a data type:

there are different data types in JS (and other programming language), understanding data-types is fundamental

the typeof function is a function to determine the typo of object (pretty big clue in the name of typeof function :wink: )


#5

darn thanks for the info . i cant even tell the difference between arrys or data type or …well yeah it seems it blew up in my face


#6

well, understanding the data types is fundamental, otherwise you won’t understand typeof

There is plenty of documentation and tutorials on data types, i am sure you can find them :slight_smile:


#7

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