【若川视野 x源码共读】第33期 | arrify 转数组 Convert a value to an array

git clone git@github.com:sindresorhus/arrify.git

"ava": "^3.15.0",
"tsd": "^0.14.0",
"xo": "^0.39.1"

"test": "xo && ava && tsd"
// &&相当于串行（上一个执行完毕后才会继续执行下一个）、&相当于并行

- xo: 对代码进行检查
- ava: 执行根目录的test.js文件中的测试用例
- tsd: 通过index.test-d.ts文件测试index.d.ts定义    

export default function arrify(value) {
    if (value === null || value === undefined) {
        return [];
    }
    if (Array.isArray(value)) {
        return value;
    }
    if (typeof value === 'string') {
        return [value];
    }
    if (typeof value[Symbol.iterator] === 'function') {
        return [...value];
    }
    return [value];
}

let iteratorArray = new Set()
iteratorArray.add(1)
iteratorArray.add('2')
iteratorArray.add(['11', 22])
console.log(iteratorArray) /// Set(3) {1, '2', Array(2)}                
console.log(typeof iteratorArray )  /// object

let obj = {
   a: 'aa',
   b: 11,
   c: 'hellowrold'
 }
 obj = {
   ...obj,
   *[Symbol.iterator]() {
     console.log(this, 'this-item')
     yield { a: 'aa' }
     yield { b: 11 }
     yield { c: 'hellowrold' }
   }
 }
 for (const item of obj) {
   console.log(item, 'item')
 }
 // {a: 'aa'} 'item'
 // {b: 11} 'item'
 // {c: 'hellowrold'} 'item'
 // 那么obj 如果调用 arrify,对于其他的Object不生效
 // 可以统一在Object.prototype[Symbol.iterator] 上实现
 console.log(arrify(obj))
 //(3) [{…}, {…}, {…}]0: {a: 'aa'}1: {b: 11}2: {c: 'hellowrold'}length: 3[[Prototype]]: Array(0)

if (typeof value[Symbol.iterator] === 'function') {
    return [...value];
}

export default function arrify<ValueType>(
        value: ValueType
    ): ValueType extends (null | undefined)
        ? [] // eslint-disable-line  @typescript-eslint/ban-types
        : ValueType extends string
            ? [string]
            : ValueType extends readonly unknown[]
                ? ValueType
                : ValueType extends Iterable<infer T>
                    ? T[]
                    : [ValueType];

class Animal {
        name: string,
        constructor(name: string) {
            this.name = name
        }
        do(): void {
            console.log('动作')
        }
    }
    class Dog extends Animal {
        constructor(name:string){
            super(name)
        }
        do(): void {
            console.log('汪汪汪')
        }  
    }
    class Cat extends Animal {
        constructor(name:string){
            super(name)
        }
        do(): void {
            console.log('喵喵喵')
        }  
    }

import test from 'ava';
import arrify from './index.js';
test('main', t => {
  t.deepEqual(arrify('foo'), ['foo']);  // 判断字符串
  t.deepEqual(arrify(new Map([[1, 2], ['a', 'b']])), [[1, 2], ['a', 'b']]);  //Map对象
  t.deepEqual(arrify(new Set([1, 2])), [1, 2]);  //Set对象
  t.deepEqual(arrify(null), []);   // null
  t.deepEqual(arrify(undefined), []);  // undefined
  const fooArray = ['foo'];
  t.is(arrify(fooArray), fooArray);  //正常的数组
});