pick(path, matcher)(data) : pick values from JSON

var person = {
  "name" : "John",
  "age" : 32,
  "kids" : [
    { "name" : "Adam", "age" : 10 },
    { "name" : "Emily", "age" : 7 }
  ],
  "relationships" : [
    { "status" : "ongoing", "with" : { "name" : "Susan" } },
    { "status" : "ended", "with" : { "name" : "Katie" } }
  ]
};

// ----- path extraction

pick("/")(person)              // => person
pick("/name")(person)          // => "John"
pick("/kids[0]/name")(person)  // => "Adam"
pick("/kids[]/name")(person)   // => ["Adam", "Emily"]

// ----- matching

pick("/relationships[*]/with/name", { "/../../status" : "ongoing" })(person)
// => "Susan"

pick("/kids[*]", { "/name" : "Adam" })(person)
// => { "name" : "Adam", "age" : 10 }

Idea

• pick(path, matcher)(value) maps value to path and returns the result if matcher accepts it

• path can be thought of as a mapper that maps value as another value selection

• matcher can be thought of as a filter that filters the selection

Paths

Paths are defined as /-separated selectors, where each selector maps the current selection to another value:

Selector	Maps to	Example
(empty)	current
field	current[field]	/name for John maps to "John"
[idx]	current[idx]	/kids[0]/name for John maps to John's first kid's name, "Adam"
..	parent	/../../status (relative to strings "Susan" and "Katie" in the example)

For convenience, field and index-style selectors can be combined in single path segment (i.e. /array[0] instead of /array/[0].

Wildcard matching

When using [idx] selector, instead of using an numerical index, you can specify a wildcard index using [\*].

This will select the first such value in current selection where the rest of the path can be selected. I.e. /kids[\*]/name would select "Adam" because "Adam" is the first kid object with a name attribute.

Wildcard matching can be used together with custom matchers to create find-style queries.

Any matching

You can also omit the index altogether and use [] matcher to filter values in current selection down to those for which the rest of the path can be selected.

/kids[]/name will thus return an array of ["Adam", "Emily"] because both kid objects contain a name attribute.

Any matching can also be used with custom matchers to create filter-style queries.