56 lines
1.9 KiB
JavaScript
56 lines
1.9 KiB
JavaScript
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define("dojo/when", [
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"./Deferred",
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"./promise/Promise"
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], function(Deferred, Promise){
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"use strict";
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// module:
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// dojo/when
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return function when(valueOrPromise, callback, errback, progback){
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// summary:
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// Transparently applies callbacks to values and/or promises.
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// description:
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// Accepts promises but also transparently handles non-promises. If no
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// callbacks are provided returns a promise, regardless of the initial
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// value. Foreign promises are converted.
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//
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// If callbacks are provided and the initial value is not a promise,
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// the callback is executed immediately with no error handling. Returns
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// a promise if the initial value is a promise, or the result of the
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// callback otherwise.
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// valueOrPromise:
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// Either a regular value or an object with a `then()` method that
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// follows the Promises/A specification.
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// callback: Function?
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// Callback to be invoked when the promise is resolved, or a non-promise
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// is received.
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// errback: Function?
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// Callback to be invoked when the promise is rejected.
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// progback: Function?
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// Callback to be invoked when the promise emits a progress update.
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// returns: dojo/promise/Promise
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// Promise, or if a callback is provided, the result of the callback.
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var receivedPromise = valueOrPromise && typeof valueOrPromise.then === "function";
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var nativePromise = receivedPromise && valueOrPromise instanceof Promise;
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if(!receivedPromise){
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if(callback){
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return callback(valueOrPromise);
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}else{
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return new Deferred().resolve(valueOrPromise);
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}
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}else if(!nativePromise){
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var deferred = new Deferred(valueOrPromise.cancel);
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valueOrPromise.then(deferred.resolve, deferred.reject, deferred.progress);
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valueOrPromise = deferred.promise;
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}
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if(callback || errback || progback){
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return valueOrPromise.then(callback, errback, progback);
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}
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return valueOrPromise;
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};
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});
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