40 lines
1.1 KiB
JavaScript
40 lines
1.1 KiB
JavaScript
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'use strict'
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const constants = require('./constants')
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const unwrapSync = require('./unwrapSync')
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// Behaves like a Promise, though the then() and catch() methods are unbound and
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// must be called with the instance as their thisArg.
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//
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// The executor must either return a value or throw a rejection reason. It is
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// not provided resolver or rejecter methods. The executor may return another
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// thenable.
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class Thenable {
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constructor (executor) {
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try {
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this.result = unwrapSync(executor())
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this.state = constants.RESOLVED
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} catch (err) {
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this.result = err
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this.state = constants.REJECTED
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}
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}
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then (onFulfilled, onRejected) {
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if (this.state === constants.RESOLVED && typeof onFulfilled === 'function') {
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return new Thenable(() => onFulfilled(this.result))
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}
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if (this.state === constants.REJECTED && typeof onRejected === 'function') {
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return new Thenable(() => onRejected(this.result))
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}
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return this
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}
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catch (onRejected) {
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return this.then(null, onRejected)
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}
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}
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module.exports = Thenable
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