postman collection host code example

Example 1: collection variables postman

Only accessible within the same collection and
can not be accessed anywhere else
COLLECTION variables are available throughout 
the requests in a collection and are independent
of environments, so do not change based on the selected environment.
I use collection variables when
I use single environment like url details.
We can refer to the variable by using {{}}(double curly brace)
and  it can be used anywhere

Example 2: defining collection variables

Use pm.collectionVariables to define a collection variable:

pm.collectionVariables.set("variable_key", "variable_value");