javascript - What is difference between assigning value to variable and storing value into variable -

i reading book object oriented javascript , found this:

reference types not store object directly variable assigned, object variable in example doesn’t contain object instance. instead, holds pointer (or reference) location in memory object exists. primary difference between objects , primitive values, primitive stored directly in variable.

my question meaning of ?

"reference types not store object directly variable assigned, object variable in example doesn’t contain object instance." ??

in image provided can see

var object1 = new object(); var object2 = object1; 

in case, have 2 variables both store reference (think of pointer) place in memory. in place object stored. if change object via 1 of references, , access via other 1 see has changed.

object1.somevariable = 'asdf'; object2.somevariable = 'newvalue'; console.log(object1.somevariable); // give 'newvalue' console.log(object2.somevariable); // give 'newvalue' 

if have scalar values, not store references, store value itself.

think of example:

var primitivestring = 'asdf'; var anotherprimitivestring = primitivestring; 

since both store value self, can change 1 of 2 strings, other 1 still contain asdf, since not reference something.

anotherprimitivestring = 'newvalue'; console.log(primitivestring); // give 'asdf' console.log(anotherprimitivestring); // give 'newvalue' 

here have jsfiddle explained example.