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pas2js: doc about await

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git-svn-id: trunk@45445 -
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Mattias Gaertner 2020-05-20 08:11:52 +00:00
parent 74e65f77bc
commit fa267f90a6
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utils/pas2js/docs/translation.html
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@ -77,6 +77,7 @@
<a href="#externalclassancestor">External class as ancestor</a><br>
<a href="#jsvalue">The JSValue type</a><br>
<a href="#bracketaccessor">Accessing JS object properties with the bracket accessor</a><br>
<a href="#async">Async/AWait</a><br>
<a href="#rtti">RTTI - Run Time Type Information</a><br>
<a href="#compilerdirectives">Compiler directives</a><br>
<a href="#othersupportedelements">Other supported Pascal elements</a><br>
@ -2721,7 +2722,7 @@ function(){
<ul>
<li><i>constructor New</i> is translated to <i>new ExtClass(params)</i>.</li>
<li><i>constructor New; external name ''GlobalFunc''</i> is translated to <i>new GlobalFunc(params)</i>.</li>
<li><i>constructor SomeName; external name <i>'{}'</i> is translated to <i>{}</i>.</li>
<li><i>constructor SomeName; external name </i>'{}'</i> is translated to <i>{}</i>.</li>
<li>Otherwise it is translated to <i>new ExtClass.FuncName(params)</i>.</li>
</ul>
@ -2988,7 +2989,84 @@ End.
If <i>o</i> is <i>nil</i> it will give a JS error.<br>
Local types (i.e. inside a procedure) do not have typeinfo.<br>
Open array parameters are not yet supported.<br>
Note that FPC <i>typeinfo(aClassVar)<i> returns the compiletime type, so it works on <i>nil</i>.<br>
Note that FPC <i>typeinfo(aClassVar)</i> returns the compiletime type, so it works on <i>nil</i>.<br>
</div>
<div class="section">
<h2 id="async">Async/AWait</h2>
Pas2js supports the JS operators async/await to simplify the use of Promise.
The await operator corresponds to two intrinsic Pas2js functions:
<ul>
<li><i>function await(const Expr: T): T;</i> // implicit promise</li>
<li><i>function await(aType; p: TJSPromise): aType;</i> // explicit promise requires the resolved type</li>
</ul>
The await function can only be used inside a procedure with the async modifier.<br>
For example:
<table class="sample">
<tbody>
<tr>
<th>Pascal</th>
<th>JavaScript</th>
</tr>
<tr>
<td>
<pre>Program MyModule;
uses JS, Web;
function ResolveAfter2Seconds: TJSPromise;
begin
Result:=TJSPromise.new(procedure(resolve, reject : TJSPromiseResolver)
begin
window.setTimeout(procedure
begin
resolve('resolved');
end,
2000); // wait 2 seconds
end);
end;
procedure AsyncCall; async;
var s: string;
begin
writeln('calling');
s := await(string,resolveAfter2Seconds());
writeln(s); // expected output: 'resolved'
end;
begin
AsyncCall;
end.
</pre>
</td>
<td>
<pre>rtl.module("program",["System","JS","Web"],function () {
"use strict";
var $mod = this;
this.ResolveAfter2Seconds = function () {
var Result = null;
Result = new Promise(function (resolve, reject) {
window.setTimeout(function () {
resolve("resolved");
},2000);
});
return Result;
};
this.AsyncCall = async function () {
var s = "";
pas.System.Writeln("calling");
s = await $mod.ResolveAfter2Seconds();
pas.System.Writeln(s);
};
$mod.$main = function () {
$mod.AsyncCall();
};
});
</pre>
</td>
</tr>
</tbody>
</table>
</div>