我不了解对象内部的传播语法 [英] I don't understand about spread syntax inside objects

问题描述

我不了解对象内部的传播语法.

I don't understand about spread syntax inside objects.

console.log(...false) // TypeError not iterable
console.log(...1) // TypeError not iterable
console.log(...null) // TypeError not iterable
console.log(...undefined) // TypeError not iterable

我了解上述代码由于没有迭代器而发生错误.

I understand above codes that occurs error because of none-iterator.

但是这些代码运行良好.

But these codes are working well.

console.log({...false}) // {}
console.log({...1}) // {}
console.log({...null}) // {}
console.log({...undefined}) // {}

请让我知道上面的代码为什么起作用.

Please let me know why the above codes are working.

推荐答案

对象传播是完全不同的.它映射到 Object.assign()

The object spread is quite different. It maps to Object.assign() internally.

因此， const a = {... 1} 与 const a = Object.assign({}，1)在这里， Object.assign({}，1)将 1 视为 object ，而不是 number .因此，您没有抛出任何异常.

So const a = {...1} is same as const a = Object.assign({}, 1) Here Object.assign({},1) has treated 1 as object not as number. Therefore, you did not get any exception thrown.

另外，如果您对数组 [... 1] 尝试了相同的操作，则应该抛出错误，因为它不会将 1 视为 object ，您将获得与 .. 1 .

Additionally if you have tried same thing for arrays [...1] it should have thrown error, since it does not treats 1 as object and you get the same behavior as ..1.

总结:

console.log({...false}) => console.log(Object.assign({}, false))
console.log({...1}) => console.log(Object.assign({}, 1))
console.log({...null}) => console.log(Object.assign({}, null))
console.log({...undefined}) => console.log(Object.assign({}, undefined))

PS: Object.assign()规格

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