如何在Node-RED中拆分JSON字符串后提取值

[{"id":"f3a2b2e8.7e4a9","type":"mqtt in","z":"c6d6b6d1.1d0d3","name":"","topic":"topic","qos":"2","datatype":"auto","broker":"a1e2a3d3.4b5c6d","x":150,"y":160,"wires":[["d7b6c5d4.3e2f1"]]},{"id":"d7b6c5d4.3e2f1","type":"json","z":"c6d6b6d1.1d0d3","name":"","property":"payload","action":"","pretty":false,"x":310,"y":160,"wires":[["e8d9c0b1.9a8b7"]]},{"id":"e8d9c0b1.9a8b7","type":"function","z":"c6d6b6d1.1d0d3","name":"","func":"var value1 = msg.payload.key1;\nvar value2 = msg.payload.key2;\n\nmsg.payload = {\n    \"value1\": value1,\n    \"value2\": value2\n};\n\nreturn msg;","outputs":1,"noerr":0,"x":470,"y":160,"wires":[["f1e0d9c8.7b6a5"]]},{"id":"f1e0d9c8.7b6a5","type":"debug","z":"c6d6b6d1.1d0d3","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":630,"y":160,"wires":[]},{"id":"a1e2a3d3.4b5c6d","type":"mqtt-broker","z":"","name":"","broker":"localhost","port":"1883","clientid":"","usetls":false,"compatmode":true,"keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","closeTopic":"","closeQos":"0","closePayload":"","willTopic":"","willQos":"0","willPayload":""}]