Little snippet how to convert element properties in array
[{"id":"83df52e9.922dc","type":"function","z":"86fb73e0.f92d","name":"","func":"var arr = [{\"timestamp\":\"123456789\",\"state\":\"true\"},\n{\"timestamp\":\"456123456\",\"state\":\"true\"},\n{\"timestamp\":\"789456\",\"state\":\"false\"},\n{\"timestamp\":\"98696546\",\"state\":\"true\"}]\nmsg.payload = arr\nreturn msg;","outputs":1,"noerr":0,"x":310,"y":220,"wires":[["6a6d94f8.ba43bc","84c46c7.1a9cf9"]]},{"id":"e98aedec.4fe99","type":"inject","z":"86fb73e0.f92d","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":160,"y":220,"wires":[["83df52e9.922dc"]]},{"id":"6a6d94f8.ba43bc","type":"function","z":"86fb73e0.f92d","name":"","func":"\nlet arr = msg.payload\nfunction fixTime(el){\n el.timestamp = parseInt(el.timestamp)\n}\narr.forEach(fixTime)\nmsg.payload = arr\nreturn msg;","outputs":1,"noerr":0,"x":460,"y":220,"wires":[["fc12428e.f3748"]]},{"id":"84c46c7.1a9cf9","type":"debug","z":"86fb73e0.f92d","name":"before","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":450,"y":180,"wires":[]},{"id":"fc12428e.f3748","type":"debug","z":"86fb73e0.f92d","name":"after","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":510,"y":280,"wires":[]}]