Cannot define custom empty elements for json2html function

[alanmtk]

Idea

It would be a nice feature being able to define custom empty elements to be handled by json2html function.

Use case

I am parsing an html block in order to make it amp valid html so among a lot of custom amp tags I have to transform img to amp-img.

Problem

json2html function is handling a predefined list of empty elements:

html2json/src/html2json.js

Lines 125 to 152 in ef49d49

	global.json2html = function json2html(json) {
	// Empty Elements - HTML 4.01
	var empty = ['area', 'base', 'basefont', 'br', 'col', 'frame', 'hr', 'img', 'input', 'isindex', 'link', 'meta', 'param', 'embed'];
	var child = '';
	if (json.child) {
	child = json.child.map(function(c) {
	return json2html(c);
	}).join('');
	}
	var attr = '';
	if (json.attr) {
	attr = Object.keys(json.attr).map(function(key) {
	var value = json.attr[key];
	if (Array.isArray(value)) value = value.join(' ');
	return key + '=' + q(value);
	}).join(' ');
	if (attr !== '') attr = ' ' + attr;
	}
	if (json.node === 'element') {
	var tag = json.tag;
	if (empty.indexOf(tag) > -1) {
	// empty element
	return '<' + json.tag + attr + '/>';
	}

After parsing my html and modifying the img tag, I want to convert it back to html so I have this situation:

Initial tag:

<img src="example.jpg"/>

Expected result:

<amp-img src="example.jpg"/>

Actual result

<amp-img src="example.jpg"></amp-img>

Proposed solution

Adding an options object to json2html so we can push our custom tags to the predefined list would be enough to make it work.

I made a pull request (#38) with the proposed solution and a test to make sure it works.