Add a variable to a class instance at runtime: Difference between revisions

=={{header|jq}}==

jq's "+" operator can be used to add a key/value pair (or to add multiple key-value pairs) to an existing object at runtime, but

jq is a functional programming language, and objects themselves cannot be altered. Thus it may be helpful to introduce a variable, since the value of a variable can in effect be updated. For example:

<lang jq>{"a":1} as $a | ($a + {"b":2}) as $a | $a

</lang>Thus the value of $a has undergone the desired transition, that is, its final value is {"a":1, "b":2}.

A Javascript-like syntax can also be used to add (or update) a key, for example:<lang jq>$a|.c = 3

# or equivalently:

$a|.["c"] = 3</lang>