javascript ImmutableJS Map() 和 fromJS() 有什么区别？
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What is the difference between ImmutableJS Map() and fromJS()?
提问by sowdri
var a = {address: {postcode: 5085}}
var b = Immutable.fromJS(a)
var c = b.setIn(['address', 'suburb'], 'broadview').toJS(); // no error
console.log(c);
var d = Immutable.Map(a);
var e = d.setIn(['address', 'suburb'], 'broadview').toJS(); // error invalid keyPath(…)
Could someone explain the difference.
有人能解释一下区别吗。
Thanks,
谢谢，
回答by Samu Joseph
In this example,
在这个例子中，
var a = {address: {postcode: 5085}}
var d = Immutable.Map(a);
Here, d.get('address')is immutable. It's value cannot change to any other objects. We can only create a new Object from the existing object using the Immutable.Map.set()function of ImmutableJS.
在这里，d.get('address')是不可变的。它的值不能更改为任何其他对象。我们只能使用Immutable.Map.set()ImmutableJS的功能从现有对象创建一个新对象。
But, the object referenced by d.get('address')i.e, {postcode:5085}is a standard JavaScript object. It is mutable. A statement like this can alter the value of postcode:
但是，ie引用d.get('address'){postcode:5085}的对象是标准的 JavaScript 对象。它是可变的。像这样的语句可以改变 的值postcode：
d.get('address').postcode=6000;
If you check the value of d again, you can see that he value has been changed.
如果再次查看d的值，可以看到他的值已经改变了。
console.log(JSON.stringify(d)); //Outputs {"address":{"postcode":6000}}
which is against the principles of immutability.
这违反了不变性原则。
The reason is that ImmutableJS data structures like Listand Mapimparts the immutability feature to only the level-1 members of the List/Map.
原因是 ImmutableJS 数据结构喜欢List并将Map不变性特性赋予List/的第 1 级成员Map。
So, if you have objects inside arrays or arrays inside objects and want them too to be immutable, your choice is Immutable.fromJS.
因此，如果您在数组内有对象或在对象内有数组并希望它们也是不可变的，那么您的选择是Immutable.fromJS.
var a = {address: {postcode: 5085}}
var b = Immutable.fromJS(a);
b.get('address').postcode=6000;
console.log(JSON.stringify(b)); //Outputs {"address":{"postcode":5085}}
From the above example you can clearly know how fromJSmakes the nested members immutable.
从上面的例子你可以清楚地知道如何fromJS使嵌套成员不可变。
I hope you understood the difference between Mapand fromJS. All the best =)
我希望你明白之间的差别Map和fromJS。一切顺利 =)
回答by timetofly
fromJSdoes a deep conversion. That is, it'll recurse through all the keys and convert all elements to Lists, Maps, etc.
fromJS进行深度转换。也就是说，它将遍历所有键并将所有元素转换为列表、地图等。
In your second example, addressis a plain object, not an ImmutableJS object, so you cannot use setInto change its value.
在您的第二个示例中，address是一个普通对象，而不是 ImmutableJS 对象，因此您不能使用setIn更改其值。
