fix(ajax): Fix case-insensitive headers in HTTP request (#4453)

In RFC 7230 and RFC 7540 is written, that HTTP headers is case-insensitive, so this is fix for correct serializing request body base on HTTP headers.

Author: DostalTomas

spec/observables/dom/ajax-spec.ts

@@ -600,6 +600,26 @@ describe('ajax', () => {
 expect(MockXMLHttpRequest.mostRecent.data).to.equal('{"🌟":"🚀"}');
 });
 
+it('should send json body not mattered on case-sensitivity of HTTP headers',()=>{
+constbody={
+hello: 'world'
+};
+
+constrequestObj={
+url: '/flibbertyJibbet',
+method: '',
+body: body,
+headers: {
+'cOnTeNt-TyPe': 'application/json; charset=UTF-8'
+}
+};
+
+ajax(requestObj).subscribe();
+
+expect(MockXMLHttpRequest.mostRecent.url).to.equal('/flibbertyJibbet');
+expect(MockXMLHttpRequest.mostRecent.data).to.equal('{"hello":"world"}');
+});
+
 it('should error if send request throws',(done: MochaDone)=>{
 constexpected=newError('xhr send failure');
 

src/internal/observable/dom/AjaxObservable.ts

@@ -202,17 +202,18 @@ export class AjaxSubscriber<T> extends Subscriber<Event> {
 constheaders=request.headers=request.headers||{};
 
 // force CORS if requested
-if(!request.crossDomain&&!headers['X-Requested-With']){
+if(!request.crossDomain&&!this.getHeader(headers,'X-Requested-With')){
 headers['X-Requested-With']='XMLHttpRequest';
 }
 
 // ensure content type is set
-if(!('Content-Type'inheaders)&&!(root.FormData&&request.bodyinstanceofroot.FormData)&&typeofrequest.body!=='undefined'){
+letcontentTypeHeader=this.getHeader(headers,'Content-Type');
+if(!contentTypeHeader&&!(root.FormData&&request.bodyinstanceofroot.FormData)&&typeofrequest.body!=='undefined'){
 headers['Content-Type']='application/x-www-form-urlencoded; charset=UTF-8';
 }
 
 // properly serialize body
-request.body=this.serializeBody(request.body,request.headers['Content-Type']);
+request.body=this.serializeBody(request.body,this.getHeader(request.headers,'Content-Type'));
 
 this.send();
 }
@@ -315,6 +316,16 @@ export class AjaxSubscriber<T> extends Subscriber<Event> {
 }
 }
 
+privategetHeader(headers: {},headerName: string): any{
+for(letkeyinheaders){
+if(key.toLowerCase()===headerName.toLowerCase()){
+returnheaders[key];
+}
+}
+
+returnundefined;
+}
+
 privatesetupEvents(xhr: XMLHttpRequest,request: AjaxRequest){
 constprogressSubscriber=request.progressSubscriber;