promise連鎖
<apex:page>
<html>
<head>
</head>
<body>
<script type="text/javascript">
Promise.resolve('foo')
// 1. Receive "foo", concatenate "bar" to it, and resolve that to the next then
.then(function(string) {
return new Promise(function(resolve, reject) {
setTimeout(function() {
string += 'bar';
resolve(string);
}, 1);
});
})
// 2. receive "foobar", register a callback function to work on that string
// and print it to the console, but not before returning the unworked on
// string to the next then
.then(function(string) {
setTimeout(function() {
string += 'baz';
console.log(string); // foobarbaz
}, 1)
return string;
})
// 3. print helpful messages about how the code in this section will be run
// before the string is actually processed by the mocked asynchronous code in the
// previous then block.
.then(function(string) {
console.log("Last Then: oops... didn't bother to instantiate and return " +
"a promise in the prior then so the sequence may be a bit " +
"surprising");
// Note that `string` will not have the 'baz' bit of it at this point. This
// is because we mocked that to happen asynchronously with a setTimeout function
console.log(string); // foobar
});
// logs, in order:
// Last Then: oops... didn't bother to instantiate and return a promise in the prior then so the sequence may be a bit surprising
// foobar
// foobarbaz
</script>
</body>
</html>
</apex:page>結果
