Javascript 类型错误：无法匹配“未定义”或“空”
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TypeError: Cannot match against 'undefined' or 'null'
提问by Prashanth Chandra
Code
代码
client.createPet(pet, (err, {name, breed, age}) => {
if (err) {
return t.error(err, 'no error')
}
t.equal(pet, {name, breed, age}, 'should be equivalent')
})
Error
错误
client.createPet(pet, (err, {name, breed, age}) => {
^
TypeError: Cannot match against 'undefined' or 'null'.
Why am I getting this error? My knowledge of ES6 led me to presume that this error should only arise if the array or object being destructured or its childrenis undefinedor null.
为什么我收到这个错误？我ES6的知识使我推测，如果只应出现此错误数组或对象被解构或者其子女是undefined或null。
I wasn't aware that function parameters are used as a match. And if they are then why is it only an error if I try to destructure one of them? (that isn't undefinedor null).
我不知道函数参数被用作匹配项。如果它们是，那么为什么我尝试解构其中一个只是一个错误？（这不是undefined或null）。
回答by thefourtheye
this error should only arise if the array or object being destructured or its children is
undefinedornull.
如果数组或对象的存在解构或其子是应该只出现此错误
undefined或null。
Exactly. In your case, the object being destructured is either undefinedor null. For example,
确切地。在您的情况下，被解构的对象是undefined或null。例如，
function test(err, {a, b, c}) {
console.log(err, a, b, c);
}
test(1, {a: 2, b: 3, c: 4});
// 1 2 3 4
test(1, {});
// 1 undefined undefined undefined
test(1);
// TypeError: Cannot match against 'undefined' or 'null'.
