[英]What is the difference between ImmutableJS Map() and fromJS()?
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. 有人可以解释这个区别。
Thanks, 谢谢,
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 . 这里,
d.get('address')
是不可变的 。 It's value cannot change to any other objects. 它的值不能改变为任何其他对象。 We can only create a new Object from the existing object using the
Immutable.Map.set()
function of ImmutableJS. 我们只能使用
Immutable.Map.set()
函数从现有对象创建一个新Object。
But, the object referenced by d.get('address')
ie, {postcode:5085}
is a standard JavaScript object. 但是,
d.get('address')
引用的对象,即{postcode:5085}
是一个标准的JavaScript对象。 It is mutable . 这是可变的 。 A statement like this can alter the value of
postcode
: 像这样的声明可以改变
postcode
的价值:
d.get('address').postcode=6000;
If you check the value of d again, you can see that he value has been changed. 如果再次检查d的值,则可以看到他的值已更改。
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 List
and Map
imparts the immutability feature to only the level-1 members of the List
/ Map
. 原因是像
List
和Map
这样的ImmutableJS数据结构只赋予List
/ Map
的level-1成员不变性特征。
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, 如果对象内部有数组或数组内的对象,并且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 fromJS
makes the nested members immutable. 从上面的例子中你可以清楚地知道
fromJS
如何使嵌套成员不可变。
I hope you understood the difference between Map
and fromJS
. 我希望你理解
Map
和fromJS
之间的区别。 All the best =) 一切顺利=)
fromJS
does a deep conversion. fromJS
做了很深的转换。 That is, it'll recurse through all the keys and convert all elements to Lists, Maps, etc. 也就是说,它将通过所有键递归并将所有元素转换为列表,地图等。
In your second example, address
is a plain object, not an ImmutableJS object, so you cannot use setIn
to change its value. 在第二个示例中,
address
是一个普通对象,而不是ImmutableJS对象,因此您不能使用setIn
来更改其值。
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