Babel plugin to transform async functions containing await expressions to the equivalent chain of Promise calls with use of minimal helper functions.

async function fetchAsObjectURL(url) {
    const response = await fetch(url);
    const blob = await response.blob();
    return URL.createObjectURL(blob);
}

var fetchAsObjectURL = _async(function(url) {
	return _await(fetch(url), function(response) {
		return _await(response.blob(), function(blob) {
			return URL.createObjectURL(blob);
		});
	});
});

• async/await
• for/while/do loops (including loops that would exhaust stack if dispatched recursively)
• switch statements (including fallthrough and default cases)
• conditional expressions
• logical expressions
• try/catch
• break/continue statements (on both loops and labeled statements)
• throw expressions
• Function hoisting
• Variable hoisting
• Arrow functions
• Methods
• arguments
• this
• Proper member dereference order of operations

• Standards-compliant event loop ordering: error path inside catch/finally clauses are always dispatched asynchronously
• Function.length: async functions will often return a length of 0 (when the _async wrapper is used)

• eval: impossible to support without deep hooks into the runtime
• Async generator functions: not implemented or planned
• Function.name: rewrite pass removes function name instrumentation
• new AsyncFunction(...): impossible to support without shipping babel and the plugin in the output