javascript - JSON.stringify如何自动将矩对象转换为iso字符串？

Question

我很好奇，像moment这样的库如何在对象上调用JSON.stringify时自动从对象转换为字符串。

此刻的示例测试:https://github.com/moment/moment/blob/3147fbc486209f0b479dc0b29672d4c2ef39cf43/src/test/moment/format.js#L144-L146

这是一些我很好奇它如何工作的示例代码

const moment = require('moment');
const duration = moment.duration(1374);
console.log('duration = ', duration); // Prints a duration object
console.log('JSON.stringify(duration) = ', JSON.stringify(duration)); // Prints a string such as `P0D1T0H3` <-- Note: Not exact value, just similar format

Answer 1

从MDN:

If the value has a toJSON() method, it's responsible to define what data will be serialized.

从 moment:

proto.toJSON         = toISOString;