import convert = require("convert-source-map");

var json = convert
	.fromComment('//@ sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoiZm9vLmpzIiwic291cmNlcyI6WyJjb25zb2xlLmxvZyhcImhpXCIpOyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiQUFBQSIsInNvdXJjZVJvb3QiOiIvIn0=')
	.toJSON();

var modified = convert
	.fromComment('//@ sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoiZm9vLmpzIiwic291cmNlcyI6WyJjb25zb2xlLmxvZyhcImhpXCIpOyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiQUFBQSIsInNvdXJjZVJvb3QiOiIvIn0=')
	.setProperty('sources', ['CONSOLE.LOG("HI");'])
	.toJSON();

console.log(json);
console.log(modified);