Immutable.js 引用相等性

Question

给出以下简单代码:

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?

对于最终的比较，我希望它返回 true，因为我将路径 ['c', 'd'] 设置为其他内容，然后返回原始值，通过结构共享，我希望它会导致 c 保留对原始数据结构的引用？

我是否误解了它的工作原理？

Answer 1

首先，这个 console.log(a.equals(b)); 实际上返回 false:

现在回答你的问题，如 Immutable.js here 中所述在“无操作优化时返回自身”子章节:

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.

有一个例子:

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);

由于您要更改值，setIn 返回一个新引用。因此，通过引用它们并不相等。

希望我有帮助:)