比较详情

• 除 NaN 外，原始值使用抽象相等比较（==）进行比较。 如果双方都是 NaN，则视为相同。
• 对象的类型标签应该是一样的。
• 仅考虑自有属性。
• Error 名称和消息总是被比较，即使它们不是可枚举的属性。
• 对象封装器作为对象和未封装的值进行比较。
• Object 属性是无序比较的。
• Map 键和 Set 项是无序比较的。
• 当双方不同或双方遇到循环引用时，则递归停止。
• 实现不测试对象的 [[Prototype]]。
• 不比较 Symbol 属性。
• WeakMap 和 WeakSet 的比较不依赖于它们的值。

以下示例不会抛出 AssertionError，因为抽象相等比较（==）认为原始值相等。

// 注意：这不会抛出 AssertionError！
assert.deepEqual('+00000000', false);

“深度”相等意味着子对象的可枚举"自有"属性也被评估：

const assert = require('assert');

const obj1 = {
  a: {
    b: 1
  }
};
const obj2 = {
  a: {
    b: 2
  }
};
const obj3 = {
  a: {
    b: 1
  }
};
const obj4 = Object.create(obj1);

assert.deepEqual(obj1, obj1);
// OK

// b 的值不同：
assert.deepEqual(obj1, obj2);
// AssertionError: { a: { b: 1 } } deepEqual { a: { b: 2 } }

assert.deepEqual(obj1, obj3);
// OK

// 原型被忽略：
assert.deepEqual(obj1, obj4);
// AssertionError: { a: { b: 1 } } deepEqual {}

如果值不相等，则抛出 AssertionError，其 message 属性设置为等于 message 参数的值。 如果未定义 message 参数，则分配默认错误消息。 如果 message 参数是 Error 的实例，则将抛出错误而不是 AssertionError。

• Primitive values are compared with the Abstract Equality Comparison ( == ) with the exception of NaN. It is treated as being identical in case both sides are NaN.
• Type tags of objects should be the same.
• Only enumerable "own" properties are considered.
• Error names and messages are always compared, even if these are not enumerable properties.
• Object wrappers are compared both as objects and unwrapped values.
• Object properties are compared unordered.
• Map keys and Set items are compared unordered.
• Recursion stops when both sides differ or both sides encounter a circular reference.
• Implementation does not test the [[Prototype]] of objects.
• Symbol properties are not compared.
• WeakMap and WeakSet comparison does not rely on their values.

The following example does not throw an AssertionError because the primitives are considered equal by the Abstract Equality Comparison ( == ).

// WARNING: This does not throw an AssertionError!
assert.deepEqual('+00000000', false);

"Deep" equality means that the enumerable "own" properties of child objects are evaluated also:

const assert = require('assert');

const obj1 = {
  a: {
    b: 1
  }
};
const obj2 = {
  a: {
    b: 2
  }
};
const obj3 = {
  a: {
    b: 1
  }
};
const obj4 = Object.create(obj1);

assert.deepEqual(obj1, obj1);
// OK

// Values of b are different:
assert.deepEqual(obj1, obj2);
// AssertionError: { a: { b: 1 } } deepEqual { a: { b: 2 } }

assert.deepEqual(obj1, obj3);
// OK

// Prototypes are ignored:
assert.deepEqual(obj1, obj4);
// AssertionError: { a: { b: 1 } } deepEqual {}

If the values are not equal, an AssertionError is thrown with a message property set equal to the value of the message parameter. If the message parameter is undefined, a default error message is assigned. If the message parameter is an instance of an Error then it will be thrown instead of the AssertionError.