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    optionpublic

    options for node.js

    An implementation of the option type, sometimes known as the maybe type.

    An instance of an option type is an optional value. Either it's none, or an instance of Some:

    var option = require("option");
     
    var some = option.some("Bob");
    var none = option.none;

    A function that returns an optional string isn't that different from a function that returns a string or null. The advantage over null is that options provide a number of functions that help with manipulating optional values.

        function greet(user) {
            return "Hello " + user.name().valueOrElse("Anonymous");
        }

    Methods

    isNone() and isSome()

    • some(value).isNone() returns false
    • some(value).isSome() returns true
    • none.isNone() returns true
    • none.isSome() returns false

    value()

    • some(value).value() returns value
    • none.value() throws an error

    map(func)

    • some(value).map(func) returns some(func(value))
    • none.map(func) returns none

    flatMap(func)

    Conventionally used when func returns another option.

    • some(value).flatMap(func) returns func(value)
    • none.flatMap(func) returns none

    filter(predicate)

    • some(value).filter(predicate) returns:
      • some(value) if predicate(value) === true
      • none if predicate(value) === false
    • none.filter(predicate) returns none

    toArray()

    • some(value).toArray() returns [some]
    • none.toArray() returns []

    orElse(other)

    If other is a function (other conventionally returning another option):

    • some(value).orElse(other) returns some(value)
    • none.orElse(other) returns other()

    If other is not a function (other conventionally being another option):

    • some(value).orElse(other) returns some(value)
    • none.orElse(other) returns other

    valueOrElse(other)

    If other is a function:

    • some(value).valueOrElse(other) returns value
    • none.valueOrElse(other) returns other()

    If other is not a function:

    • some(value).valueOrElse(other) returns value
    • none.valueOrElse(other) returns other

    Functions

    option.isOption(value)

    • option.isOption(value) returns true if value is option.none or option.some(x).

    option.fromNullable(value)

    • If value is null or undefined, option.fromNullable(value) returns option.none.
    • Otherwise, returns option.some(value). For instance, option.fromNullable(5) returns option.some(5).

    Installation

    npm install option
    

    Keywords

    install

    npm i option

    Downloadsweekly downloads

    2,159

    version

    0.2.4

    license

    BSD-2-Clause

    repository

    githubgithub

    last publish

    collaborators

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