Quickly chain method calls, property access and functions in natural left to right expression
Quickly chain method calls, property access and functions in natural left to right expression.
Install and use under Node:
npm install functional-pipeline --savevar fp = require('functional-pipeline');// orglobal.fpDebug = true;var fp = require('functional-pipeline');// loads debug version of functional pipeline with// stricter argument checking and better error reporting
Install and use in browser using bower:
bower install functional-pipeline<script src="bower_components/functional-pipeline/fp.js"></script>// or<script src="bower_components/functional-pipeline/fp-debug.js"></script>// attaches as window.fp object
Assuming this common code:
return 3 * x;return x + 2;var data =age: 10return thisage;;
You can express in single line
var pipeline = fp'getAge' triple add2;
what usually takes several compositions that are read from inside out
Clear code is good code. Functional pipeline makes reading code slightly easier:
- Reading chained pipeline left to right is natural.
- Having no branches (they should be encapsulated inside functions) lowers complexity
- Composing multiple small functions makes code easier to test
I especially recommend using functional pipelines for callbacks, replacing code with prebuilt and testable pipelines.
Example: lets sort objects in the collection by date nested 2 levels deep. This is typical of the code arriving from the back end for example. Below each operation I am showing its order in the callback function. The actual argument name item does not matter.
items = _sortByitemsreturn itemlatest_eventdatetime;------ -------- ------------ --------4 3 1 2;
new Dateobject from result of the previous step
- Return the created date.
Reading the steps left to right starting in the middle, then switching to reading them right to left going back at the start of the line is unnatural to me. Here is the same sequence using functional-pipeline. The return operation is implicit.
return a;items = _sortByitems fp'latest_event' 'datetime' newDate;-------------- ---------- -------1 2 3
You could use my d3-helpers library that
provides both functional pipeline and a few small utility functions like
Creating chains of calls dynamically using strings instead of actual functions makes debugging harder. Functional pipeline has second implementation with debugging turned on. This adds stringent checks before calling a method, or executing a function or returning a non-existent property. For example:
functional-pipeline debug script first performs existance check during pipeline construction, making sure every argument is either a string or a valid function. If not, a detailed error message is thrown.
var fp = require'./node_modules/functional-pipeline/fp-debug.js';var f = fp'foo' bar; // bar is non existent function// throws right awayError: Invalid arguments to functional pipeline - not a string or function0: string foo1: undefined argument
There are also checks during pipeline execution, throwing detailed error message if something goes wrong. Both the pipeline setup and the original object is in the exception's message in addition to the immediate error cause.
var obj =bar:baz: 'baz';var pipeline = fp'bar' 'foo';pipelineobj;Error: Cannot use property foo from object"baz": "baz"pipeline0: string bar1: string foooriginal object"bar":"baz": "baz"
Author: Gleb Bahmutov © 2014
License: MIT - do anything with the code, but don't blame me if it does not work.
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Copyright (c) 2014 Gleb Bahmutov
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