When does JS create an object wrapper for a string?

Question

Symbol.iterator in 'retularString' // error right-hand side of in sould be an object

Symbol.iterator in new String() // true

Does that mean JS creates object wrappers for strings only when it calls methods / or accesses corresponding properties on them like 'string'.toUppercase() / 'string'.length?

score 3 · Accepted Answer · answered Nov 13 '18 at 07:22

3

Does that mean JS creates object wrappers for strings only when it calls methods / or accesses corresponding properties on them like 'string'.toUppercase() / 'string'.length?

Yes.

When you have a string declared as var foo = 'foo' its type is the primitive string, having no properties inherently, but when you try and access a property on it, the primitive is wrapped momentarily in the String object through a process called implicit coercion.

See this article for a full explanation of coercion in JavaScript.

answered Nov 13 '18 at 07:22

FThompson

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Perhaps the answers to this question are a good addition: https://stackoverflow.com/q/17256182/10245948 – Hero Wanders Nov 13 '18 at 07:47
I just wanted to be sure that's wrapping does not occur upon any other circumstances. – daGo Nov 13 '18 at 08:00

When does JS create an object wrapper for a string?

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