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JavaScript JavaScript Basics (Retired) Working With Numbers The Math Object

Posted by Lee Zamastil
Lee Zamastil
21,628 Points

Strings and numbers are objects? This video says "yes". Other sources say "no".

Dave says "JavaScript is made up of different types of objects. Numbers are one type of object and strings are another type of object."

My understanding (from a different course, I believe) is that numbers, strings and booleans are not objects. They are primitive values. As I'm working to keep these terms defined, this causes some confusion. What's the story?

2 Answers

Jennifer Nordell
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Jennifer Nordell
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Jennifer Nordell
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Jennifer Nordell
Treehouse Teacher

You are correct! And so is he! :smiley: Those are primitive data types in JavaScript. However, JavaScript also has corresponding object wrappers for each of these. So wherever you're seeing this, they must be referring to the object "wrapper" for that data type. Here's some information from MDN.

https://developer.mozilla.org/en-US/docs/Glossary/Primitive

Lee Zamastil
Lee Zamastil
21,628 Points

Thanks for the link. This is to the point and previously unknown to me — Except for null and undefined, all primitive values have object equivalents that wrap around the primitive values.

When strings are referred to as objects, it is here that the object wrapper is in play. Without the object wrapper it's a primitive data type. Correct?

Jennifer Nordell
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Jennifer Nordell
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Jennifer Nordell
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Jennifer Nordell
Treehouse Teacher

Lee Zamastil That's my understanding. But I'm not sure that in JavaScript they can really be separated. However you can use valueOf() to determine the primitive datatype of the ... whatever... you're looking at :smiley:

Lee Zamastil
Lee Zamastil
21,628 Points
Lee Zamastil
Lee Zamastil
21,628 Points

I'm reading Nicholas Zakas's The Principles of Object-Oriented JavaScript. In it he includes a very illustrative example of what a primitive wrapper is doing behind the scenes.

This is the code we write which allows us to ignore the fact that a primitive value is not an object and therefore does not have methods to call:

var name = "Nicholas";
var firstChar = name.charAt(0);
console.log(firstChar);                 // "N"

This is what happens behind the scenes:

// what the JavaScript engine does
var name = "Nicholas";
var temp = new String(name);
var firstChar = temp.charAt(0);
temp = null;
console.log(firstChar);                 // "N"

Zakas writes "The String object exists only for one statement before it’s destroyed (a process called autoboxing)."