3fn 中文文档教程

Question

Three-Way Comparison Function (3fn)

创建一个回调，通过一个或多个键比较两个对象。

Installation

需要 Node.js 8.3.0 或更高版本。

npm i 3fn

API

该模块导出单个函数。

Parameters

1. Variadic/Optional: sortBy (function, array, or any): A Map/object key. An array will be interpreted as a chain of nested keys. A function will be interpreted as a three-way comparison callback that accepts two arguments and returns a number. If the key is user-provided, you should wrap it in an array; otherwise you’ll have problems if the key is a function, array, or plain object.
2. Optional: options (plain object): An argument passed to the 3 and kget modules, allowing you to set their options. The most commonly-needed option is inObj, which must be set to true if sortBy is a key which points to an inherited object property.

Return Value

接受 Map、Object 或其他集合作为其参数并返回 -1、0 或 1 的回调函数。 例如，此回调然后可以传递给数组的 sort 函数。

Examples

Compare By Key

const threeFn = require('3fn')

const personA = {name: 'John'}
const personB = {name: 'Andrew'}

const compare = threeFn('name')

compare(personA, personB) // 1
compare(personB, personA) // -1

[personA, personB].sort(compare) // [personB, personA]

Compare By Inherited Key

const threeFn = require('3fn')

const _name = Symbol('name')

class Person {
  constructor (name) {
    this[_name] = name
  }

  get name () {
    return this[_name]
  }
}

const personA = new Person('John')
const personB = new Person('Andrew')

const compare = threeFn('name', {inObj: true})

compare(personA, personB) // 1
compare(personB, personA) // -1

[personA, personB].sort(compare) // [personB, personA]

Compare By Multiple Keys

const threeFn = require('3fn')

const personA = {name: 'John', age: 46}
const personB = {name: 'John', age: 27}

const compare = threeFn('name', 'age') // Sort by name first, and by age second

compare(personA, personB) // 1
compare(personB, personA) // -1

[personA, personB].sort(compare) // [personB, personA]

Compare By Nested Keys

const threeFn = require('3fn')

const personA = {name: {first: 'John'}}
const personB = {name: {first: 'Andrew'}}

const compare = threeFn(['name', 'first'])

compare(personA, personB) // 1
compare(personB, personA) // -1

[personA, personB].sort(compare) // [personB, personA]

Related

该模块基于3，三向比较模块。

它也是 fn 模块系列的一部分：

• efn: Extracted Function
• ffn: Filtering Function
• jfn: Joined Function
• mfn: Memoized Function
• ofn: Overloaded Function
• pfn: Possible Function
• qfn: Qualified Function
• vfn: Variadic Function
• wfn: Wrapper Function
• xfn: Extended Function