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index.js
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index.js
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"use strict";
class P extends Promise {
catch(predicate, cb) {
if (!cb) {
return super.catch(predicate);
}
return super.catch(err => {
if (predicate.prototype instanceof Error) {
if (err instanceof predicate) {
return cb(err);
}
} else if (predicate(err)) {
return cb(err);
}
return P.reject(err);
});
}
return(val) {
return this.then(() => val);
}
call(fn) {
const args = new Array(arguments.length - 1);
for (let i = 0; i < args.length; i++) {
args[i] = arguments[i + 1];
}
return this.then(res => res[fn].apply(res, args));
}
tap(fn) {
return this.then(res => {
return P
.resolve(fn(res))
.then(() => res);
});
}
toCallback(cb) {
return this
.then(res => cb(null, res))
.catch(err => cb(err));
}
delay(ms) {
return this.then(res => new P(resolve => setTimeout(() => resolve(res), ms)));
}
map(fn, opts) {
const concurrency = opts && opts.concurrency;
if (typeof concurrency !== "number" || !isFinite(concurrency) || concurrency < 1) {
return this.then(res => P.all(res.map(fn)));
}
return this.then(res => {
const ds = res.map(P.defer);
let i = concurrency;
ds.slice(0, concurrency).forEach(d => d.resolve());
return P.all(res.map((x, j) => {
return ds[j].promise
.then(() => fn(x, j, res))
.tap(() => ds[i] && ds[i++].resolve());
}));
});
}
filter(fn, opts) {
return this
.map((x, i, a) => P.all([fn(x, i, a), x]), opts)
.then(res => res.filter(t => t[0]).map(t => t[1]));
}
reduce(fn, initialValue) {
const reducer = (y, x, i, a) => P.resolve(y).then(z => fn(z, x, i, a));
const args = arguments.length > 1 ? [reducer, initialValue] : [reducer];
return this.then(res => res.reduce.apply(res, args));
}
forEach(fn) {
return this
.reduce((y, x, i, a) => fn(x, i, a), null)
.return(undefined);
}
// Methods should also be available as static
static defer() {
let resolve = null;
let reject = null;
const promise = new P((res, rej) => {
resolve = res;
reject = rej;
});
return { resolve, reject, promise };
}
static delay(ms, val) {
return P.resolve(val).delay(ms);
}
static map(val, fn, opts) {
const p = Array.isArray(val) ? P.all(val) : P.resolve(val);
return p.map(fn, opts);
}
static filter(val, fn, opts) {
const p = Array.isArray(val) ? P.all(val) : P.resolve(val);
return p.filter(fn, opts);
}
static reduce(val, fn, initialValue) {
const p = Array.isArray(val) ? P.all(val) : P.resolve(val);
return arguments.length > 2 ? p.reduce(fn, initialValue) : p.reduce(fn);
}
static forEach(val, fn) {
const p = Array.isArray(val) ? P.all(val) : P.resolve(val);
return p.forEach(fn);
}
static props(o) {
const keys = Object.keys(o);
return P
.map(keys, k => o[k])
.then(res => res.reduce((y, x, i) => Object.assign(y, {
[keys[i]] : x
}), {}));
}
static promisify(fn, ctx) {
return function promisifedMethod() {
return new P((resolve, reject) => {
const args = new Array(arguments.length + 1);
args[arguments.length] = function promisifedMethodCallback(err) {
if (err) {
return reject(err);
}
if (arguments.length < 3) {
return resolve(arguments[1]);
}
const res = new Array(arguments.length - 1);
for (let i = 0; i < res.length; i++) {
res[i] = arguments[i + 1];
}
return resolve(res);
};
for (let i = 0; i < arguments.length; i++) {
args[i] = arguments[i];
}
fn.apply(ctx || this, args);
});
};
}
static promisifyAll(obj, opts) {
const suffix = opts && Object.hasOwnProperty.call(opts, "suffix") ? opts.suffix : "Async";
const filter = (opts && opts.filter) || (() => true);
return Object
.keys(obj)
.filter(fn => typeof obj[fn] === "function")
.filter(fn => filter(fn, obj[fn], obj))
.reduce((y, fn) => Object.assign(y, {
[`${fn}${suffix}`] : P.promisify(obj[fn])
}), obj);
}
static try(fn) {
try {
return P.resolve(fn());
} catch (err) {
return P.reject(err);
}
}
static method(fn) {
return function promisifedMethod() {
return P.try(() => fn.apply(this, arguments));
};
}
static fromCallback(fn) {
return P.promisify(fn)();
}
// NOTE: Cannot use `util.inherits` with ES6 classes
static extend(APromise) {
// Instance methods
Object
.getOwnPropertyNames(P.prototype)
.filter(k => k !== "constructor")
.reduce((y, k) => Object.assign(y, {
[k] : P.prototype[k]
}), APromise.prototype);
// Static methods
return Object
.getOwnPropertyNames(P)
.filter(k => ["length", "name", "prototype"].indexOf(k) < 0)
.reduce((y, k) => Object.assign(y, {
[k] : P[k]
}), APromise);
}
}
module.exports = P;