jlafer-fnal-util

This is a collection of utility functions that I find useful when working with objects, arrays and dates.

NOTE: documentation of functions to follow. So...if you stumbled across this package and were planning on using it - buyer beware. Perhaps better is to look at the source on GitHub and see/copy the code.

Installation

npm install --save jlafer-fnal-util

Helper Functions

kvListToObj

kvListToObj :: (string, string) -> [object] -> object

This HOF takes two strings -- representing the keys of property keys and their values -- and will create a function that transforms an array of such key-value objects into an object with a property for each item. It is useful for mapping an array of properties into a dictionary object.

  const props = [
    {name: 'name', value: 'size'},
    {name: 'type', value: 'string'},
    {name: 'descr', value: 'product size'}
  ];
  const nameValueListToObj = kvListToObj('name', 'value');
  nameValueListToObj(props)  //-> {name: 'size', type: 'string', descr: 'product size'}

makeMapFirstOfPairFn

makeMapFirstOfPairFn :: mapFn -> pair -> pair

This HOF takes a mapper and will create a function that, given a pair (i.e., an array of length two), will transform the first element of the pair. It is useful for mapping an array of pairs - often one created from an object's keys and values.

  const strings = ['hdr', 'My Heading'];
  const mapFirstToUpper = makeMapFirstOfPairFn(R.toUpper);
  mapFirstToUpper(strings)  //-> ['HDR', 'My Heading']

mapKeysOfObject

mapKeysOfObject :: mapFirstOfPairFn -> object -> object

This HOF takes a mapper and will create a function that will transform all keys of an object. The supplied mapper function must transform the first element of a pair array. Such a mapper can be made with the makeMapFirstOfPairFn HOF.

  const strings = {
    header: 'My Header',
    body: 'My Body',
    footer: 'My Footer'
  };
  const mapFirstToUpper = makeMapFirstOfPairFn(R.toUpper);
  const mapKeysToUpper = mapKeysOfObject(mapFirstToUpper);
  mapKeysToUpper(strings) //-> {HEADER: 'My Header', BODY: 'My Body', FOOTER: 'My Footer'}

pickNamesAndValues

pickNamesAndValues :: [object] -> object

Given an array of objects, each of which contains name and value properties, this function will return an object having the name values as keys, with associated values taken from the corresponding input value values.

const input = [
  {name: 'length', value: 10},
  {name: 'datatype', value: 'string'}
];
pickNamesAndValues(input)  //=> {length: 10, datatype: 'string'}

valueIsObject

valueIsObject :: a -> boolean

valueIsObject({foo: 'bar'})  //=> true
valueIsObject(42)  //=> false
valueIsObject([42, 43])  //=> false

valueNotObject

valueNotObject :: a -> boolean

valueNotObject(42)  //=> true
valueNotObject([42, 43])  //=> true
valueNotObject({foo: 'bar'})  //=> false

valueIsArray

valueIsArray :: a -> boolean

valueIsArray([])  //-> true
valueIsArray([1, 2, 3])  //-> true
valueIsArray({foo: 'bar'})  //-> false

isNotNil

isNotNil :: a -> boolean

isNotNil(42) //-> true
isNotNil({}) //-> true
isNotNil([]) //-> true
isNotNil(null) //-> false

isNotEquals

isNotEquals :: a -> b -> boolean

isNotEquals(42, 43) //-> true
isNotEquals(42, null) //-> true
isNotEquals(42, 21*2) //-> false
isNotEquals('foobar', 'foo'+'bar') //-> false

isoDateToMsec

isoDateToMsec :: isoString -> integer

  const date1 = new Date(Date.UTC(1970, 0, 1, 0, 0, 0));
  isoDateToMsec(date1.toISOString()) //-> 0
  const date2 = new Date('December 17, 1990 00:00:00');
  isoDateToMsec(date2) //-> 661420800000

dtToIsoLocal

dtToIsoLocal :: [Date || isoString] -> isoString

  const date1 = new Date('December 17, 2018 00:00:00');
  dtToIsoLocal(date1) //-> '2018-12-17T00:00:00-08:00'

sumProps

sumProps :: object -> number

const quarterSales = {q1: 100, q2: 90, q3: 120, q4: 130};
sumProps(quarterSales);  //=> 440
const noSales = {};
sumProps(noSales);  //=> 0

getKeyOfMaxProp

getKeyOfMaxProp :: object -> string

const quarterSales = {q1: 100, q2: 90, q3: 120, q4: 130};
getKeyOfMaxProp(quarterSales);  //=> 130
const noSales = {};
getKeyOfMaxProp(noSales);  //=> ''