jsonpadding

Light JSONP wrapper for Node and the browser.

Features

• ES6-Promise-based (though conventional last-argument callback can be supplied)
• Built-in Promise.all-type functionality
• CommonJS/Node support (assuming global document or options includes document)
• Produces only one global, JSONP. Any auto-generated callback names are (temporarily) added to it rather than to the global scope.
• Avoids need for manually specifying conventional [?&]callback= in JSONP URLs though also allows manual specification of the name (e.g., for when the JSONP script does not accept a dynamic callback parameter) optionally resolved to a parent object and optionally renaming the parameter name itself from the conventional "callback" parameter name.
• Allows specifying a map of parameters to encode.
• Allows fine-tuned tweaking of the placement, attributes, and removal of the generated script tag and auto-generated callbacks.
• Provides facility for use in JSONP documents to retrieve the supplied callback name dynamically without server-side substitutions.
• Allows specification of timeout limits to cause a Promise rejection upon unsuccessful expirations as well as an errorHandler to override the default passing of a generic error object to Promise rejections.

Full signature

JSONP(urlStringOrArrayOfURLs, [options], [params], [callback]).then((result) => {});

or with the first argument as an object:

JSONP({url, options, params, callback}).then((result) => {});

One may omit any but the first argument:

JSONP('//example.com/url1').then((response1) => {
  // Do something with response1
});

Example usage

One may also supply the URLs as an array to get a Promise.all concurrency behavior.

JSONP([
  '//example.com/url1',
  '//example.com/url2'
]).then(([response1, response2]) => {
  // Do something with responses
});

One may alternatively supply a callback for the traditional callback style:

JSONP(url, function (data, resolve, reject) {
  // Do something with "data" and optionally call resolve or reject to continue the promise chain
});

Options

The most likely options for the user to desire any alteration are errorHandler, timeout, and possibly callbackName in case one needs to manually specify the callback name (i.e., instead of relying on the internally-used auto-generated callback name and its supplying of the response to the then function).

• appendTo - A string selector indicator the element to which one will append script tags. Defaults to document.body if available or document.head otherwise. To force the head or body, just set this to head or body.
• attrs - Map of attributes to set on the inserted script element. Note that async is set to true by default. Defaults to null.
• callbackName - Dot-separated string indicating path relative to callbackParent (or global) object. Defaults to the string "JSONP.__JSONP__<id>" where id is an auto-incrementing ID starting at 0.
• callbackParam - String to be appended to URL for (dynamic) JSON-P to indicate a callback name will follow. If set to the empty string, the entire callback key-value pair will be omitted. Defaults to "callback".
• callbackParent - Object on which to resolve callbackName. Defaults to the global scope (e.g., window, self, or this).
• document - DOM Document object on which to run queries and create elements. Defaults to global document.
• errorHandler - Callback if there are any errors loading the script element. Passed error object and reject. Defaults to a callback that rejects with a generic error message.
• params - Alternative to and takes precedence over any params argument.
• removeCallBack - Boolean on whether to remove any auto-generated callbacks. Defaults to true.
• removeScript - Boolean on whether to remove the script tag when executed. Defaults to true.
• timeout - If a number is given, the time after which to err. Defaults to false

Utility methods

The following utilities could be useful in JSONP documents wishing to retrieve the URL-supplied callback name dynamically.

JSONP.executeCallback

This method will execute a callback dictated by the name indicated by callbackParam, which is supplied in an optional options object as the second argument (and which defaults to "callback"). The parameter value should be a dot-separated path relative to baseObject or the global object if none is supplied.

Note that this method should only be run after JSONP has been executed and race conditions should be avoided by ensuring the code runs at the top of the script (as it is designed).

JSONP.executeCallback(obj, {baseObject, callbackParam} = {callbackParam: 'callback'});

So if the URL of the script were http://example.com/?callback=someClass.someMethod, then the following:

JSONP.executeCallback({test: 'Hello'});

would be equivalent to:

someClass.someMethod({test: 'Hello'});

JSONP.findParentAndChildOfMethod

This utility is used internally by JSONP and JSONP.executeCallback. It accepts a dot-separated string as a callbackName path and an optional baseObject and retrieves the immediate parent of the callback as the first item in the returned array and the string name of the child method as the second.

const [parent, child] = JSONP.findParentAndChildOfMethod(callbackName /* , baseObject */);
parent[child]();

Installation

npm install jsonpadding

import JSONP from './node_modules/jsonpadding/dist/index.js';

Credits

• Original code adapted from WebReflection
• Subsequent inspiration from simple-load-script and jsonp-es6

To-dos

• Full coverage