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