Angular 6 类型错误：无法读取未定义(读取"长度")错误的属性

Question

createToken() {
this._tokenService
.getAuth(this.userId, this.token)
.subscribe(res => 
{}, 
error => {
console.log(error);
});
}
getAuth(upn, token) {
var param = {
Upn: upn,
Token: token
};
console.log(param);

return this._http.post(
this.REST_API_ADDR + "auth", 
param, 
this.getAuthRequestHeader()
);
}
getAuthRequestHeader() {
console.log("header");
const authHeaders = new HttpHeaders({
'Content-Type':'application/json',
});
return { headers: authHeaders };
}

尝试getAuth请求来存储令牌。该请求不调用API并抛出错误。

TypeError:无法读取未定义的属性(读取"length"(在HttpHeaders.push../node_modules/@angular/common/fism5/http.js.HttpHeaders.applyUpdate(网址：http.js:199(网址：http.js:170在Array.forEach((在HttpHeaders.push../node_modules/@angular/common/fism5/http.js.HttpHeaders.init(js:170(在HttpHeaders.push../node_modules/@angular/common/fism5/http.js.HttpHeaders.forEach(js:235(在Observable_订阅(http.js:1435(在Observable.push../node_modules/rxjs/\esm5/internal/Observable.js.Observable._trySubscribe(Observable.js:42(在Observable.push../node_modules/rxjs/\esm5/internal/Observable.js.Obsubscribe(Observable.js:28(在MapOperator.push../node_modules/rxjs/_esm5/internal/operators/map.js.MapOperator.call(map.js:18(在Observable.push../node_modules/rxjs/\esm5/internal/Observable.js.Obsubscribe(Observable.js:23(

你能告诉我发生这个错误时要检查哪个部分吗？此外，如果你知道错误的原因以及如何解决，请告诉我。

Answer 1

这里描述并解决了该错误：https://github.com/angular/angular/issues/18743#issuecomment-367742057

基本上，您的头具有未定义/null值。您应该检查传递给请求的头选项。