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A higher order function is a function that takes one or more functions as arguments, or returns a function as its result.

These functions are powerful because they allow you to abstract and compose operations in a flexible and reusable way. They are a fundamental concept in functional programming.

Common examples of higher order functions are .map(), .filter(), and reducer().

.map(): Takes a function as an argument and applies it to each element in an array, returning a new array with the results.

const numbers = [1, 2, 3, 4];
const doubled = numbers.map(num => num * 2);
console.log(doubled); // [2, 4, 6, 8]

References

Namaste JS, FreeCodeCamp

Below are the different types of states that can exist within an application. There are three main types:

1. Local State

Local state pertains to a single component. An example of this would be listening to user input in a field or toggling a “show more details” button. Typically, local state is managed within the component using useState or useReducer.

2. Cross-Component State

Cross-component state impacts multiple components. For instance, managing the open/closed state of a modal overlay. While this can also be managed using useState or useReducer, it often involves passing state between components via props drilling.

3. App-Wide State

App-wide state influences the entire application, such as themes or user authentication status. Similar to cross-component state, this can be managed using useState or useReducer, albeit with the assistance of props drilling.

The LISTAGG analytic function, introduced in Oracle 11g Release 2, greatly simplifies string aggregations within SQL queries.

SELECT pid, LISTAGG(ColumnName, ' ' ) WITHIN GROUP (ORDER BY seq) AS ColumnName
FROM B GROUP BY pid;

However, if the output of the above query exceeds 4000 characters, it triggers an error, specifically ORA-01489, indicating that the result of string concatenation is too long.

To address this limitation, Oracle Database Release 2 (12.2) enhanced LISTAGG with the ability to handle overflow errors gracefully, as demonstrated below:

SELECT pid, LISTAGG(ColumnName, ' ' ON OVERFLOW TRUNCATE ) WITHIN GROUP (ORDER BY seq) AS ColumnName
FROM B GROUP BY pid;

In this updated syntax, the output is restricted to 4000 characters, preventing the ORA-01489 error from being raised.

The ON OVERFLOW clause offers several options to manage overflow situations:

• ON OVERFLOW ERROR: This is the default behavior, triggering an error if the result overflows.
• ON OVERFLOW TRUNCATE 'StringYouLike': Appends ‘StringYouLike(Count)’ at the end of the truncated string.
• ON OVERFLOW TRUNCATE '': Displays the first 4000 characters without any additional terminating string.
• ON OVERFLOW TRUNCATE WITH COUNT: Appends the total character count at the end, for example, ‘…(5512)’.

References

Stack Overflow.