HTML and CSS Reference
In-Depth Information
An immutable object is an object that cannot be changed after it is first created.
Even when these appear to change, as in the examples below, in reality a new
object is being created.
In order to see immutability in action, declare a new variable called t , and assign it the
value of s :
> t = s
"Hello world"
We can now print out the value of t , and also confirm that t and s are equal:
> t
"Hello world"
> s == t
What should happen if we now modify the string held against the variable s ? We can ap-
pend to the string value using the += operator:
> s += 'test'
"Hello worldtest"
If you now print out the value of s you will see that the string's value appears to have
> s
"Hello worldtest"
Despite this, if you print out the value of t it has retained its old value:
Search WWH ::

Custom Search