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This is an enhanced _.pick that runs validation expressions on picked attributes.

It's common for API developers to use underscore or lodash's pick to extract only the desired attributes of an incoming object when turning it into a JSON blob for storage in a database or whatever. The problem with that is that additional code is needed to verify that the attributes are actually the types that you expect them to be. Using pedantic-pick will allow you to kill two birds with one stone, so to speak.


The function signature looks much like the one you're already used to: pick(object, [expressions...], [thisArg])

In addition to the standard usage of _.pick

pick({name: 'moe', age: 50, userid: 'moe1'}, 'name', 'age')
=> {name: 'moe', age: 50} can do this with pedantic-pick:

pick({name: 'moe', age: 50, userid: 'moe1'}, '!string::name', 'number::age')
=> {name: 'moe', age: 50}

or, of course, use the shorthand form:

pick({name: 'moe', age: 50, userid: 'moe1'}, '!s::name', 'n::age')
=> {name: 'moe', age: 50}

and when something doesn't pass your rules an error is thrown (protip: use try/catch):

pick({name: 'moe', age: 50, userid: 'moe1'}, '!s::name', '!alias')
=> Error: alias failed validation


Each given expression argument must conform to this "grammar": [!][validator::]key


The following validators are built-in (and later we'll accept custom validation functions as arguments):

  • required (prefix the expression with !)
  • number (or num or n)
  • boolean (or bool or b)
  • function (or fun or f)
  • object (or o)
  • string (or s)
  • array (or a)
  • nempstring (non-empty string; or nes)
  • nemparray (non-empty array; or nea)