Comparison with ScriptRunner for Jira Server
You can refer to the Differences between ScriptRunner for Jira Server and Jira Cloud page, which highlights details on Feature Parity, including the JQL query comparison table.
Although you may be familiar with advanced queries in the Jira Server version of ScriptRunner, the Cloud infrastructure differs and, therefore, some queries are not available or are implemented differently. Even if you have a good understanding of JQL Functions from Jira Server, it's worth noting that some of the concepts here are a little different.
As it is not possible to integrate directly into the standard search functionality that Jira Cloud provides, the ScriptRunner Enhanced Search functionality provides the ability to run advanced JQL functions in your Jira filters in a similar way to ScriptRunner for Jira Server. You can read more details on the differences in the JQL Query Comparison information.
It is not possible in Jira Cloud for an add-on to alter the results of a JQL search either during or after a search is being performed.
Differences
If you want to use a custom field, you can use either field key customfield_10500 or field name e.g. 'StoryPoints'. Custom field names are likely to have spaces, which can’t be parsed. If so, remove the spaces. It’s not case-sensitive but use camel-case for maximum readability. If your field names have any other punctuation you must use the format customfield_10500.
When you specify regular expressions, you don’t have to escape backslash characters. Example: write \d+ instead of \\d+
Unsupported Functions
Compared to ScriptRunner for Jira Server, we cannot deliver the functions described below.
myProjects/recentProjects
We are not able to support queries that are based on user-specific data.
aggregateExpression
At this time we are not implementing this function.