core.es5.js：1020错误TypeError：res.json不是一个函数

Question

控制台错误：有人可以帮助我解决此问题吗？我使用的是Angular4。预先致谢

core.es5.js:1020 ERROR TypeError: res.json is not a function
    at MapSubscriber.project (http-loader.js:17)
    at MapSubscriber.webpackJsonp.../../../../rxjs/operators/map.js.MapSubscriber._next (map.js:79)
    at MapSubscriber.webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next (Subscriber.js:93)
    at MapSubscriber.webpackJsonp.../../../../rxjs/operators/map.js.MapSubscriber._next (map.js:85)
    at MapSubscriber.webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next (Subscriber.js:93)
    at FilterSubscriber.webpackJsonp.../../../../rxjs/operators/filter.js.FilterSubscriber._next (filter.js:89)
    at FilterSubscriber.webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next (Subscriber.js:93)
    at MergeMapSubscriber.webpackJsonp.../../../../rxjs/operators/mergeMap.js.MergeMapSubscriber.notifyNext (mergeMap.js:145)
    at InnerSubscriber.webpackJsonp.../../../../rxjs/InnerSubscriber.js.InnerSubscriber._next (InnerSubscriber.js:23)
    at InnerSubscriber.webpackJsonp.../../../../rxjs/Subscriber.js.Subscriber.next (Subscriber.js:93)