https://harald.ist.org/paste/error_handling.html
1<!DOCTYPE html><html lang="en" tabindex="0"><head><meta charset="UTF-8"><script>
2function reject_caught () {
3 return new Promise( (resolve, reject)=>{
4 console.log( "\n\nFailing with a caught rejection:" );
5 reject( "SOFT ERROR" );
6 }).catch( (result)=>{
7 if (result instanceof Error) {
8 throw result;
9 } else {
10 console.log( "REJECTED:", result );
11 }
12 });
13}
14
15function reject_uncaught () {
16 return new Promise( (resolve, reject)=>{
17 console.log( "\n\nFailing with an uncaught rejection:" );
18 reject( "SOFT ERROR" );
19 })
20}
21
22function fail_caught () {
23 return new Promise( (resolve, reject)=>{
24 console.log( "\n\nFailing with a caught error:" );
25 HARD_ERROR();
26 }).catch( (result)=>{
27 if (result instanceof Error) {
28 throw result;
29 } else {
30 console.log( "REJECTED:", result );
31 }
32 });
33}
34
35function fail_uncaught () {
36 return new Promise( (resolve, reject)=>{
37 console.log( "\n\nFailing with an uncaught error:" );
38 HARD_ERROR();
39 })
40}
41
42function fail_normally () {
43 console.log( "\n\nFailing normally:" );
44 HARD_ERROR();
45}
46
47function show_error (event) {
48 var message;
49
50 //console.log( event );
51
52 if (typeof event.reason == "string") {
53 message = event.reason;
54 } else {
55 switch (event.type) {
56 case "error" : message = event.error.message; break;
57 case "unhandledrejection" : message = event.reason.message; break;
58 default : message = "Failed at failing";
59 }
60 }
61
62 console.log( "FAIL:", message );
63 event.preventDefault();
64}
65
66
67addEventListener( "load", ()=>{
68 addEventListener( "error", show_error );
69 addEventListener( "unhandledrejection", show_error );
70
71 setTimeout( reject_caught, 0 );
72 setTimeout( reject_uncaught, 100 );
73 setTimeout( fail_caught, 200 );
74 setTimeout( fail_uncaught, 300 );
75 setTimeout( fail_normally, 400 );
76});
77</script></head><body><h1>Error Test</h1>
78</body></html>

Every program ends, but not all of them halt.

Error Test