54 lines
1.8 KiB
Markdown
54 lines
1.8 KiB
Markdown
|
# sigmund
|
||
|
|
|
||
|
|
Quick and dirty signatures for Objects.
|
||
|
|
|
||
|
|
This is like a much faster `deepEquals` comparison, which returns a
|
||
|
|
string key suitable for caches and the like.
|
||
|
|
|
||
|
|
## Usage
|
||
|
|
|
||
|
|
```javascript
|
||
|
|
function doSomething (someObj) {
|
||
|
|
var key = sigmund(someObj, maxDepth) // max depth defaults to 10
|
||
|
|
var cached = cache.get(key)
|
||
|
|
if (cached) return cached
|
||
|
|
|
||
|
|
var result = expensiveCalculation(someObj)
|
||
|
|
cache.set(key, result)
|
||
|
|
return result
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
The resulting key will be as unique and reproducible as calling
|
||
|
|
`JSON.stringify` or `util.inspect` on the object, but is much faster.
|
||
|
|
In order to achieve this speed, some differences are glossed over.
|
||
|
|
For example, the object `{0:'foo'}` will be treated identically to the
|
||
|
|
array `['foo']`.
|
||
|
|
|
||
|
|
Also, just as there is no way to summon the soul from the scribblings
|
||
|
|
of a cocaine-addled psychoanalyst, there is no way to revive the object
|
||
|
|
from the signature string that sigmund gives you. In fact, it's
|
||
|
|
barely even readable.
|
||
|
|
|
||
|
|
As with `util.inspect` and `JSON.stringify`, larger objects will
|
||
|
|
produce larger signature strings.
|
||
|
|
|
||
|
|
Because sigmund is a bit less strict than the more thorough
|
||
|
|
alternatives, the strings will be shorter, and also there is a
|
||
|
|
slightly higher chance for collisions. For example, these objects
|
||
|
|
have the same signature:
|
||
|
|
|
||
|
|
var obj1 = {a:'b',c:/def/,g:['h','i',{j:'',k:'l'}]}
|
||
|
|
var obj2 = {a:'b',c:'/def/',g:['h','i','{jkl']}
|
||
|
|
|
||
|
|
Like a good Freudian, sigmund is most effective when you already have
|
||
|
|
some understanding of what you're looking for. It can help you help
|
||
|
|
yourself, but you must be willing to do some work as well.
|
||
|
|
|
||
|
|
Cycles are handled, and cyclical objects are silently omitted (though
|
||
|
|
the key is included in the signature output.)
|
||
|
|
|
||
|
|
The second argument is the maximum depth, which defaults to 10,
|
||
|
|
because that is the maximum object traversal depth covered by most
|
||
|
|
insurance carriers.
|