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Promise.js
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Promise.js
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import { isFunction, isObjectType } from 'utils/is';
import { base } from 'config/environment';
/* istanbul ignore if */
if (!base.Promise) {
const PENDING = {};
const FULFILLED = {};
const REJECTED = {};
const Promise = (base.Promise = function(callback) {
const fulfilledHandlers = [];
const rejectedHandlers = [];
let state = PENDING;
let result;
let dispatchHandlers;
const makeResolver = newState => {
return function(value) {
if (state !== PENDING) return;
result = value;
state = newState;
dispatchHandlers = makeDispatcher(
state === FULFILLED ? fulfilledHandlers : rejectedHandlers,
result
);
wait(dispatchHandlers);
};
};
const fulfill = makeResolver(FULFILLED);
const reject = makeResolver(REJECTED);
try {
callback(fulfill, reject);
} catch (err) {
reject(err);
}
return {
// `then()` returns a Promise - 2.2.7
then(onFulfilled, onRejected) {
const promise2 = new Promise((fulfill, reject) => {
const processResolutionHandler = (handler, handlers, forward) => {
if (isFunction(handler)) {
handlers.push(p1result => {
try {
resolve(promise2, handler(p1result), fulfill, reject);
} catch (err) {
reject(err);
}
});
} else {
handlers.push(forward);
}
};
processResolutionHandler(onFulfilled, fulfilledHandlers, fulfill);
processResolutionHandler(onRejected, rejectedHandlers, reject);
if (state !== PENDING) {
wait(dispatchHandlers);
}
});
return promise2;
},
catch(onRejected) {
return this.then(null, onRejected);
},
finally(callback) {
return this.then(
v => {
callback();
return v;
},
e => {
callback();
throw e;
}
);
}
};
});
Promise.all = function(promises) {
return new Promise((fulfill, reject) => {
const result = [];
let pending;
let i;
if (!promises.length) {
fulfill(result);
return;
}
const processPromise = (promise, i) => {
if (promise && isFunction(promise.then)) {
promise.then(value => {
result[i] = value;
--pending || fulfill(result);
}, reject);
} else {
result[i] = promise;
--pending || fulfill(result);
}
};
pending = i = promises.length;
while (i--) {
processPromise(promises[i], i);
}
});
};
Promise.race = function(promises) {
return new Promise((fulfill, reject) => {
let pending = true;
function ok(v) {
if (!pending) return;
pending = false;
fulfill(v);
}
function fail(e) {
if (!pending) return;
pending = false;
reject(e);
}
for (let i = 0; i < promises.length; i++) {
if (promises[i] && isFunction(promises[i].then)) {
promises[i].then(ok, fail);
}
}
});
};
Promise.resolve = function(value) {
if (value && isFunction(value.then)) return value;
return new Promise(fulfill => {
fulfill(value);
});
};
Promise.reject = function(reason) {
if (reason && isFunction(reason.then)) return reason;
return new Promise((fulfill, reject) => {
reject(reason);
});
};
// TODO use MutationObservers or something to simulate setImmediate
const wait = function(callback) {
setTimeout(callback, 0);
};
const makeDispatcher = function(handlers, result) {
return function() {
for (let handler; (handler = handlers.shift()); ) {
handler(result);
}
};
};
const resolve = function(promise, x, fulfil, reject) {
let then;
if (x === promise) {
throw new TypeError(`A promise's fulfillment handler cannot return the same promise`);
}
if (x instanceof Promise) {
x.then(fulfil, reject);
} else if (x && (isObjectType(x) || isFunction(x))) {
try {
then = x.then;
} catch (e) {
reject(e);
return;
}
if (isFunction(then)) {
let called;
const resolvePromise = function(y) {
if (called) return;
called = true;
resolve(promise, y, fulfil, reject);
};
const rejectPromise = function(r) {
if (called) return;
called = true;
reject(r);
};
try {
then.call(x, resolvePromise, rejectPromise);
} catch (e) {
if (!called) {
reject(e);
called = true;
return;
}
}
} else {
fulfil(x);
}
} else {
fulfil(x);
}
};
}