postman using interpolation code example

Example 1: how to define variables in api

-Use pm.globals to define a global variable:

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

-Use pm.collectionVariables to
define a collection variable:

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

-Use pm.environment to define an environment
variable (in the currently selected environment):

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

-You can use unset to remove a variable:
pm.environment.unset("variable_key");

-Defining local variables
Local variables are temporary values you set
in your request scripts using the following syntax:

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

Example 2: how to access variables in api

You can use double curly braces to reference variables
throughout the Postman user interface. For example,
to reference a variable named "username" in your request 
auth settings, you could use the following syntax with 
double curly braces around the name:

{{username}}