Val

Val class wraps value.

Installation

$ npm i @js-commons/val

or

$ yarn add @js-commons/val

Use in your script

const Val = require('@js-commons/val')

or

import Val from '@js-commons/val'

API

You can use below methods.

Creation

Val.empty()

const val = Val.empty()
console.log(val) // { $value: null }

Val.of(value)

const val = Val.of('foo')
console.log(val) // { $value: 'foo' }

Intermediate operation

Val.filter(callback)

const val = Val.of('foo')
const filtered = val.filter(v => v.startsWith('f'))
console.log(filtered) // { $value: 'foo' }

const val = Val.of('foo')
const filtered = val.filter(v => v.startsWith('b'))
console.log(filtered) // { $value: null }

Val.map(callback)

const val = Val.of('foo')
const mapped = val.map(v => v + '_')
console.log(mapped) // { $value: 'foo_' }

const val = Val.empty()
const mapped = val.map(v => v + '_')
console.log(mapped) // { $value: null }

Val.ifPresent(callback)

const val = Val.of('foo')
let tmp
const val2 = val.ifPresent(v => {
  tmp = v
})
console.log(val2) // { $value: 'foo' }
console.log(tmp) // foo

const val = Val.empty()
let tmp
const val2 = val.ifPresent(v => {
  tmp = v
})
console.log(val2) // { $value: null }
console.log(tmp) // undefined

Val.ifAbsent(callback)

const val = Val.of('foo')
let tmp
const val2 = val.ifAbsent(() => {
  tmp = 'bar'
})
console.log(val2) // { $value: 'foo' }
console.log(tmp) // undefined

const val = Val.empty()
let tmp
const val2 = val.ifAbsent(() => {
  tmp = 'bar'
})
console.log(val2) // { $value: null }
console.log(tmp) // bar

Terminal operation

Val.or(value)

const val = Val.of('foo')
const value = val.or('bar')
console.log(value) // foo

const val = Val.empty()
const value = val.or('bar')
console.log(value) // bar

Val.orGet(callback)

const val = Val.of('foo')
const value = val.orGet(() => 'bar')
console.log(value) // foo

const val = Val.empty()
const value = val.orGet(() => 'bar')
console.log(value) // bar

Val.matches(callback)

const val = Val.of('foo')
console.log(val.matches(v => v === 'foo')) // true

const val = Val.of('foo')
console.log(val.matches(v => v === 'bar')) // false

Val.is(value)

const val = Val.of('foo')
console.log(val.is('foo')) // true

const val = Val.of('foo')
console.log(val.is('bar')) // false

Val.isPresent()

const val = Val.of('foo')
console.log(val.isPresent()) // true

const val = Val.empty()
console.log(val.isPresent()) // false

Val.isAbsent()

const val = Val.of('foo')
console.log(val.isAbsent()) // false

const val = Val.empty()
console.log(val.isAbsent()) // true