Implement promises.promisify() without bluebird

Author: mwilliamson

lib/docx/files.js

@@ -15,7 +15,7 @@ exports.uriToPath = uriToPath;
 function Files(base) {
     function read(uri, encoding) {
         return resolveUri(uri).then(function(path) {
-            return readFile(path, encoding).caught(function(error) {
+            return readFile(path, encoding).catch(function(error) {
                 var message = "could not open external image: '" + uri + "' (document directory: '" + base + "')\n" + error.message;
                 return Promise.reject(new Error(message));
             });

lib/promises.js

@@ -4,7 +4,7 @@ var bluebird = require("bluebird/js/release/promise")();
 exports.defer = defer;
 exports.extend = extend;
 exports.props = props;
-exports.promisify = bluebird.promisify;
+exports.promisify = promisify;
 exports.attempt = attempt;
 exports.forEachSeries = forEachSeries;
 exports.toExternalPromise = toExternalPromise;
@@ -24,6 +24,23 @@ exports.nfcall = function(func) {
     });
 };
 
+function promisify(func) {
+    return function() {
+        var args = Array.prototype.slice.call(arguments);
+
+        return new Promise(function(resolve, reject) {
+            args.push(function(error, value) {
+                if (error) {
+                    reject(error);
+                } else {
+                    resolve(value);
+                }
+            });
+            func.apply(null, args);
+        });
+    };
+}
+
 function props(obj) {
     // We rely on .keys() and .values() returning properties in the same order.
     var keys = Object.keys(obj);