将 Map 转换为 JavaScript 对象

Question

所以我得到了以下 JavaScript，其中包含一个键/值对，用于将嵌套路径映射到目录。

function createPaths(aliases, propName, path) {
    aliases.set(propName, path);
}

map = new Map();

createPaths(map, 'paths.aliases.server.entry', 'src/test');
createPaths(map, 'paths.aliases.dist.entry', 'dist/test');

现在我想做的是根据地图中的键创建一个 JSON 对象。

必须是，

paths: {
  aliases: {
    server: {
      entry: 'src/test'
    },
    dist: {
      entry: 'dist/test'
    }
  }
}

不确定是否有现成的方法可以做到这一点。如有任何帮助，我们将不胜感激。

Answer 1

在 MDN 中给出，

fromEntries()

自 Node v12 起可用：

const map1 = new Map([
  ['foo', 'bar'],
  ['baz', 42]
]);

const obj = Object.fromEntries(map1);
// { foo: 'bar', baz: 42 }

将对象转换回地图：

const map2 = new Map(Object.entries(obj));
// Map(2) { 'foo' => 'bar', 'baz' => 42 }

Answer 2

仅使用 ES6 方式

1. Object.fromEntries

const log = console.log;

const map = new Map();
// undefined
map.set(`a`, 1);
// Map(1) {"a" => 1}
map.set(`b`, 2);
// Map(1) {"a" => 1, "b" => 2}
map.set(`c`, 3);
// Map(2) {"a" => 1, "b" => 2, "c" => 3}

// Object.fromEntries ✅
const obj = Object.fromEntries(map);

log(`\nobj`, obj);
// obj { a: 1, b: 2, c: 3 }

2. ...spread

   &

   destructuring assignment

const log = console.log;

const map = new Map();
// undefined
map.set(`a`, 1);
// Map(1) {"a" => 1}
map.set(`b`, 2);
// Map(1) {"a" => 1, "b" => 2}
map.set(`c`, 3);
// Map(2) {"a" => 1, "b" => 2, "c" => 3}

const autoConvertMapToObject = (map) => {
  const obj = {};
  for (const item of [...map]) {
    const [
      key,
      value
    ] = item;
    obj[key] = value;
  }
  return obj;
}

const obj = autoConvertMapToObject(map)

log(`\nobj`, obj);
// obj { a: 1, b: 2, c: 3 }

参考

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment

https://2ality.com/2015/08/es6-map-json.html

Answer 3

我希望这个功能足够不言自明。这就是我以前做的工作。

/*
 * Turn the map<String, Object> to an Object so it can be converted to JSON
 */
function mapToObj(inputMap) {
    let obj = {};

    inputMap.forEach(function(value, key){
        obj[key] = value
    });

    return obj;
}


JSON.stringify(returnedObject)

Answer 4

您可以循环遍历地图和键并分配值

function createPaths(aliases, propName, path) {
    aliases.set(propName, path);
}

var map = new Map(),
    object = {};

createPaths(map, 'paths.aliases.server.entry', 'src/test');
createPaths(map, 'paths.aliases.dist.entry', 'dist/test');

map.forEach((value, key) => {
    var keys = key.split('.'),
        last = keys.pop();
    keys.reduce((r, a) => r[a] = r[a] || {}, object)[last] = value;
});

console.log(object);

Answer 5

另一种方法。我很好奇哪个性能更好，但 jsPerf 下降了:(。

var obj = {};

function createPaths(map, path, value)
{
	if(typeof path === "string") path = path.split(".");
	
	if(path.length == 1)
	{
		map[path[0]] = value;
		return;
	}
	else
	{
		if(!(path[0] in map)) map[path[0]] = {};
		return createPaths(map[path[0]], path.slice(1), value);
	}
}

createPaths(obj, 'paths.aliases.server.entry', 'src/test');
createPaths(obj, 'paths.aliases.dist.entry', 'dist/test');

console.log(obj);

没有递归：

var obj = {};

function createPaths(map, path, value)
{
    var map = map;
    var path = path.split(".");
    for(var i = 0, numPath = path.length - 1; i < numPath; ++i)
    {
        if(!(path[i] in map)) map[path[i]] = {};
        map = map[path[i]];
    }
    map[path[i]] = value;
}

createPaths(obj, 'paths.aliases.server.entry', 'src/test');
createPaths(obj, 'paths.aliases.dist.entry', 'dist/test');
createPaths(obj, 'paths.aliases.dist.dingo', 'dist/test');
createPaths(obj, 'paths.bingo.dist.entry', 'dist/test');

console.log(obj);

var obj = {};

function createPaths(map, path, value)
{
    var map = map;
    var path = path.split(".");
    
    while(path.length > 1)
    {
        map = map[path[0]] = map[path.shift()] || {};
    }
    
    map[path.shift()] = value;
  
}

createPaths(obj, 'paths.aliases.server.entry', 'src/test');
createPaths(obj, 'paths.aliases.dist.entry', 'dist/test');
createPaths(obj, 'paths.aliases.dist.dingo', 'dist/test');
createPaths(obj, 'paths.bingo.dist.entry', 'dist/test');

console.log(obj);

Answer 6

var items = {1:"apple",2:"orange",3:"pineapple"};
let map = new Map(Object.entries(items)); //object to map
console.log(map);
const obj = new Object();
map.forEach((value,key)=> obj[key]=value);  // map to object
console.log(obj);

Answer 7

let myMap = new Map();
myMap.set('key1', 'value1');
myMap.set('key2', 'value2');

// Convert Map to Object
let myObject = {};
for (let [key, value] of myMap) {
  myObject[key] = value;
}

console.log(myObject); // { key1: 'value1', key2: 'value2' }

方法2

Copy code
const obj = {
  key1: 'value1',
  key2: 'value2'
};

const newMap = new Map(Object.entries(obj));

console.log(newMap);