84 lines
2.7 KiB
JavaScript
84 lines
2.7 KiB
JavaScript
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"use strict";
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Object.defineProperty(exports, "__esModule", {
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value: true
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});
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// Symbols is a better way to do this, but not all browsers have good support,
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// so instead we'll just make do with a very unlikely string.
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var customArgumentsToken = "__ES6-PROMISIFY--CUSTOM-ARGUMENTS__";
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/**
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* promisify()
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* Transforms callback-based function -- func(arg1, arg2 .. argN, callback) -- into
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* an ES6-compatible Promise. Promisify provides a default callback of the form (error, result)
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* and rejects when `error` is truthy.
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*
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* @param {function} original - The function to promisify
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* @return {function} A promisified version of `original`
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*/
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function promisify(original) {
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// Ensure the argument is a function
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if (typeof original !== "function") {
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throw new TypeError("Argument to promisify must be a function");
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}
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// If the user has asked us to decode argument names for them, honour that
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var argumentNames = original[customArgumentsToken];
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// If the user has supplied a custom Promise implementation, use it. Otherwise
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// fall back to whatever we can find on the global object.
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var ES6Promise = promisify.Promise || Promise;
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// If we can find no Promise implemention, then fail now.
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if (typeof ES6Promise !== "function") {
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throw new Error("No Promise implementation found; do you need a polyfill?");
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}
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return function () {
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var _this = this;
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for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
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args[_key] = arguments[_key];
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}
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return new ES6Promise(function (resolve, reject) {
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// Append the callback bound to the context
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args.push(function callback(err) {
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if (err) {
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return reject(err);
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}
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for (var _len2 = arguments.length, values = Array(_len2 > 1 ? _len2 - 1 : 0), _key2 = 1; _key2 < _len2; _key2++) {
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values[_key2 - 1] = arguments[_key2];
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}
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if (values.length === 1 || !argumentNames) {
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return resolve(values[0]);
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}
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var o = {};
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values.forEach(function (value, index) {
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var name = argumentNames[index];
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if (name) {
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o[name] = value;
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}
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});
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resolve(o);
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});
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// Call the function.
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original.call.apply(original, [_this].concat(args));
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});
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};
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}
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// Attach this symbol to the exported function, so users can use it
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promisify.argumentNames = customArgumentsToken;
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promisify.Promise = undefined;
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// Export the public API
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exports.promisify = promisify;
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