README
magic-hook
Extends functions with pre hooks.
Installation
npm i -S magic-hook
Usage
You can add pre hooks to extend your methods.
'use strict'
var hook = require('magic-hook')
// The target function
function concat(a, b) {
return a + b
}
// The hooked function
var hookedConcat = hook(concat)
// A pre hook
var msgNo = 0
function counterHook(next, a, b) {
return next('concatenation #' + (++msgNo) + ': ' + a, b)
}
hookedConcat.pre(counterHook)
for (var i = 3; i--;) console.log(hookedConcat('Hello ', 'world!'))
//> concatenation #1: Hello world!
//> concatenation #2: Hello world!
//> concatenation #3: Hello world!
Hooks can be removed using removePre:
hookedConcat.removePre(counterHook)
console.log(hookedConcat('Hello ', 'world!'))
//> Hello world!
To remove all pres associated with a hook just call removePre with no arguments:
hookedConcat.removePre()
To abort the target function's execution just
don't call the next function in the pre hook:
hookedConcat.pre(function(next) {
return 'The original function was overwritten';
})
console.log(hookedConcat("Doesn't matter what goes here"))
//> The original function was overwritten
You can overwrite the target function's result as well:
var hookedSum = hook(function(a, b) { return a + b; })
hookedSum.pre(function(sum, a, b) {
if (a === 1 && b === 1) return 3
return sum(a, b)
})
console.log(hookedSum(2, 2))
//> 4
console.log(hookedSum(1, 1))
//> 3
Motivation
Suppose you have an object with a save method.
It would be nice to be able to declare code that runs before save.
For example, you might want to run validation code before every save.
Or you might want to create plugins that will modify the input parameters of
your save method.