Immutable.js 引用相等

Question

给定以下简单代码：

const Immutable = require('immutable');
const a = Immutable.fromJS({
    a: 1,
    b: [2, 3, 4],
    c: {
        d: 1
    }
});
const b = a.setIn(['c', 'd'], "Something else");
const c = b.setIn(['c', 'd'], 1);

console.log(a.equals(b)); // true
console.log(Immutable.is(a, c)); // true
console.log(a === c); // false?

对于最后的比较，我希望它 return 正确，因为我将路径 ['c', 'd'] 设置为其他内容，然后返回原始值，并且通过结构共享我会期望它导致 c 持有对原始数据结构的引用吗？

我是否误解了它的工作原理？

Answer 1

第一，这个console.log(a.equals(b));returns其实是假的：

现在回答您的问题，如 Immutable.js here 的 "Return self on no-op optimization" 子章所述：

When possible, Immutable.js avoids creating new objects for updates where no change in value occurred, to allow for efficient reference equality checking to quickly determine if no change occurred.

有那个例子：

const { Map } = require('immutable');
const originalMap = Map({ a: 1, b: 2, c: 3 });
const updatedMap = originalMap.set('b', 2);
updatedMap === originalMap; // No-op .set() returned the original reference.

However updates which do result in a change will return a new reference. Each of these operations occur independently, so two similar updates will not return the same reference:

那个例子：

const { Map } = require('immutable');
const originalMap = Map({ a: 1, b: 2, c: 3 });
const updatedMap = originalMap.set('b', 1000);
// New instance, leaving the original immutable.
updatedMap !== originalMap;
const anotherUpdatedMap = originalMap.set('b', 1000);
// Despite both the results of the same operation, each created a new reference.
anotherUpdatedMap !== updatedMap;
// However the two are value equal.
anotherUpdatedMap.equals(updatedMap);

由于您正在更改值，setIn returns 一个新的参考。因此它们在引用上不相等。

希望我有所帮助:)

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