adding a custom type, typeMap is frozen

[dkebler]

Little help please, I'd like to do this.

mytypechecker.js

let tc = require('typechecker')

// add custom types
tc.isBuffer = function isBuffer(obj) {
  return !!obj.constructor && typeof obj.constructor.isBuffer === 'function' && obj.constructor.isBuffer(obj)
}

// add map entries for custom types
tc.typeMap.buffer = tc.isBuffer

module.exports = tc

that might work but can't try it because the typeMap object is frozen.

Not sure why this was done (save fools from themselves?)

So how can I add my custom types to the library so I can use getTypes without having to pass it an additional map every time

i.e. don't want to do this every time.
expect(u.getType(Buffer.from('this is a test'), { buffer: u.isBuffer })).to.equal('buffer')

if typeMap needs to be frozen why bother to export it? How about not and providing a registration function to register additional custom types for use with getType?

Thx.

[balupton]

Modifying typeMap directly would also change functionality for other packages that use typechecker which could cause problems.

However, getType accepts a second parameter that can be a type map, so you could do the following:

// custom-typechecker.js
const typechecker = require('typechecker')
const customTypeChecker = Object.assign({}, typechecker)

const customTypeMap = {
	array: typechecker.isArray,
	boolean: typechecker.isBoolean,
	date: typechecker.isDate,
	error: typechecker.isError,
	class: typechecker.isClass,
	function: typechecker.isFunction,
	null: typechecker.isNull,
	number: typechecker.isNumber,
	regexp: typechecker.isRegExp,
	string: typechecker.isString,
	'undefined': typechecker.isUndefined,
	buffer: Buffer.isBuffer,  // must be before isObject, as otherwise isObject will catch it
	map: typechecker.isMap,
	weakmap: typechecker.isWeakMap,
	object: typechecker.isObject
}

customTypeChecker.getType = function customGetType (value, _typeMap) {
	return typechecker.getType(value, _typeMap || customTypeMap)
}

module.exports = customTypeChecker

// app.js
var result = require('./custom-typechecker.js').getType(Buffer.from(''))
console.log(result)  // buffer

[dkebler]

That didn't work as written. customTypeMap is neither exported nor passed into the new getType. I tried a few variations on this to no avail.

Did you mean this??
customTypeChecker.typeMap = {
would just overwrite the frozen type map and then nothing need be done to getTypes.

I tried that and that still fails. Got time to get this working for yourself first? I'll write a pr for the readme once it's working.

  it('Should include custom types', function () {
    expect(u.isBuffer(Buffer.from('this is a test'))).to.equal(true)
    expect(u.getType(Buffer.from('this is a test'))).to.equal('buffer')
  })

  1) Variable Types Library -  Should include custom types:

      AssertionError: expected 'object' to equal 'buffer'
      + expected - actual

      -object
      +buffer

[balupton]

Update previous example, should work.

[balupton]

@dkebler okay, my updated code should work, but there is a bug in typechecker, so I'll update the code

[balupton]

@dkebler okay, v4.4.1 is fixed, which makes the above work

[balupton]

the customTypeMap definition could also be done like so:

// Add our custom types
const customTypeMap = {
	buffer: Buffer.isBuffer
}
// Add original types
Object.keys(typechecker.typeMap).forEach(function (key) {
	customTypeMap[key] = customTypeMap[key] || typechecker.typeMap[key]
})

[dkebler]

@balupton thanks! Now I can all add my classes as types :-).

I definitely preferred merging the maps (cleaner) but your object.keys statement above wasn't doing it. So here is the final working module. I'll do a PR for the readme and add this with some explanation.
again thx.

//mytypechecker.js

const typechecker = require('typechecker')
const customTypeChecker = Object.assign({}, typechecker)

// add custom types, a key and corresponding function for each
customTypeChecker.isBuffer = function isBuffer(obj) {
  return !!obj.constructor && typeof obj.constructor.isBuffer === 'function' && obj.constructor.isBuffer(obj)
}

// Create a custom type map and make an key/property for each new type 
// the key/property used will be the string returned by getType. 
let customTypeMap = {
  buffer: customTypeChecker.isBuffer
}

// merge base typeMap with customTypeMap
customTypeMap = Object.assign(customTypeMap, customTypeChecker.typeMap)

//overwrite getType to use customTypeMap if available
customTypeChecker.getType = function customGetType(value, _typeMap) {
  return typechecker.getType(value, _typeMap || customTypeMap)
}

module.exports = customTypeChecker

[balupton]

Glad it works :-)

I definitely preferred merging the maps (cleaner) but your object.keys statement above wasn't doing it.

Whoops fixed.