Consider the following example:
var prom1 = new Promise(function(resolve, reject) {
setTimeout(function() {
console.log("Promise executed");
reject("Rejected");
}, 2000);
});
console.log("Before Promise");
var test = prom1.then(function(data) {
console.log(data, 1);
return data;
}); //skipping onReject handeler
window.addEventListener("unhandledrejection", function() {
console.log("unhandledrejection");
});In this case unhandledrejection fired, because we skipped the onReject handler in the then function. So far, everything as expected. Now let's consider another example, where I completly omit the then handler.
var prom2 = new Promise(function(resolve, reject) {
setTimeout(function() {
console.log("Promise executed");
reject("Rejected");
}, 2000);
});
console.log("Before Promise2");
//skipping onReject handeler, because we skip the whole "then" method.
window.addEventListener("unhandledrejection", function() {
console.log("unhandledrejection");
});Now both the scripts give same output, but if you save this code in html file and open without a server(no localhost), e.g. as file:///C:/Users/test/index.html you will see that unhandledrejection didn't execute this time. Why is that?
P.S: I have tested on my windows 10 Chrome Version 107.0.5304.88 (Official Build) (64-bit), Firefox version 106.0.5 (64 bit), Edge Version 107.0.1418.35 (Official build) (64-bit) and Opera latest version.
P.S2: As aksed in the comments, I have added the whole html file. I had no idea that in file:// protocol my own javascript files are considerd cross origin:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script src="js/script.js"></script>
</body>
</html>
