While searching for the source code of express router, I came across this interesting piece:
var debug = require('debug')('express:router:route');
I am curious to know more about this unusual way of passing arguments. Can someone explain it?
While searching for the source code of express router, I came across this interesting piece:
var debug = require('debug')('express:router:route');
I am curious to know more about this unusual way of passing arguments. Can someone explain it?
Within the realm of Javascript, functions hold a special status as they are deemed "first class", allowing them to be maneuvered like any other data value.
The require('debug') command fetches a function. To clarify, the primary export from the debug npm module is a function and not an object.
This particular function is then invoked with the argument of "express:router:route".
Partial application, as elucidated on Wikipedia, involves passing some state or configuration to obtain a function that corresponds to said state or config. Although this scenario may seem like partial application at first glance, it simply operates as a shortened version of:
var debug = require('debug');
debug('express:router:route');
The usage of require should not be misconstrued as intended for partial application purposes. Rather, it signifies that the debug package returns a function, which is promptly executed in its place.
Currying is a powerful technique found in functional programming where a function with multiple arguments can be transformed into a series of nested functions. This allows you to pass the arguments one by one, creating a new function each time until all arguments are utilized.
While it may seem complex at first, delving into currying is definitely worth the effort.
Exploring Currying:
Currying, as a concept in functional programming, involves breaking down a function with several arguments into a chain of functions that take one argument at a time. Each subsequent function produced expects the next argument in line until all arguments are processed. Through closure, these arguments remain accessible and are employed when the final function in the curried sequence is invoked.
For further insights, visit:
Have you checked out the debug package (link)?
The
debugpackage provides a convenient function; by passing the name of your module to this function, you will receive an enhanced version ofconsole.errorto use for debug statements. This feature allows you to easily control and toggle debug output for different sections of your module and the module overall.
When you call require('debug'), you are essentially retrieving a function. You can execute this function by using require('debug')(some parameter). This enables actions like the example provided in the debug documentation:
var debug = require('debug')('http')
With this line of code, the variable debug now holds the outcome of calling the function from require('debug') with the input of 'http'.
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