Demos of two possible level loading syntaxes.

Flow.js

// Less pretty syntax, super simple to implement, generic reusable implementation
flow.exec(
	function () {
		new Entity().addComponent('level', this)
	},
	function (err, level) {
		level.addComponent('level-segment', 'something.json', this)
	},
	function (err, level) {
		level.addComponent('level-segment', 'something-else.json', this)
	},
	function (err, level) {
		renderer.draw(level);
	}
);

Hackery.js

// Nicer syntax, but the implementation is bound to the solution 
var map = new Entity()
	.addComponent('level')
	.addComponent('level-segment', 'something.json')
	.addComponent('level-segment', 'something-else.json')
	.triggers(function () {
		renderer.map(map);
	});

something-else.js

new Entity()
	.exec(
		function (entity) {
			entity.addComponent('level', entity, this)
		},
		function (entity) {
			entity.addComponent('level-segment', 'something.json', this)
		},
		function (entity) {
			entity.addComponent('level-segment', 'something-else.json', this)
		},
		function (entity) {
			renderer.draw(entity);
		}
	);