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Extraction Library

Tree Extraction for JavaScript Object Graphs

Extraction is a small JavaScript library for extracting object trees from arbitrary object graphs. Object graphs usually have cycles and contain many information. Hence, the clue is that the extracted object trees use links to break object reference cycles and can be just partial by leaving out non-requested information. The tree extraction is controlled with a custom JSON-style query language. The object tree is structurally derived from the object graph, but contains no references to the original objects and hence can be further mutated by the caller. The Extraction library is intended for two main use cases: primarily, to support the generation of responses in REST APIs based on object graphs (where the cycle problem and the partial information problem has to be resolved) and, secondarily, to support the persisting and restoring of arbitrary in-memory object graph structures (where the cycle problem has to be resolved, too). See the Github source code for more documentation and download options via NPM and Bower.

Small Demo

Your object graph (JavaScript):  
var Graph = {
    Person: [
        { id: 7,   name: "God",   tags: [ "good", "nice" ] },
        { id: 666, name: "Devil", tags: [ "bad", "cruel" ] }
    ],
    Location: [
        { id: 0,   name: "World" },
        { id: 1,   name: "Heaven" },
        { id: 999, name: "Hell" }
    ]
}

Graph.Person[0].home    = Graph.Location[1]
Graph.Person[1].home    = Graph.Location[2]

Graph.Person[1].rival   = Graph.Person[0]
Graph.Person[0].rival   = Graph.Person[1]

Graph.Location[1].owner = Graph.Person[0]
Graph.Location[2].owner = Graph.Person[1]

Graph.Location[0].subs  = [ Graph.Location[1],
                            Graph.Location[2] ]
                
Your extraction query (DSL):  
Your extracted tree (JSON):  

Copyright © 2015-2019 Dr. Ralf S. Engelschall
Available under MIT distribution license.