參考 https://tutorials.webduino.io/zh-tw/docs/socket/useful/exchange-node-red.html
解析匯率網頁
因為要抓取幣值匯率，第一個想到的就是台灣銀行的牌告匯率 ( http://rate.bot.com.tw/xrt?Lang=zh-TW )。
https://rate.bot.com.tw/xrt?Lang=zh-TW
接著按右鍵打開網頁原始碼，看一下我們要的匯率在哪裡，例如我想要抓取日幣現金匯率，那麼就要看到日幣的這個欄位。
接著我們把這段 class 複製下來，這是待會解析網頁時需要抓取的名稱。
搜尋 rate-content-cash.text-right.print_hide
透過
http request 節點來抓取 Opendata，這邊也是一樣的做法，透過 http request 抓取整個牌告匯率網頁，然後透過 html 節點篩選出特定內容，由 function 節點做分析，最後將結果由 debug 顯示出來。
inject node設定
http request 設定
https://rate.bot.com.tw/xrt?Lang=zh-TW
點選
http request 打開設定，於 URL 的地方填入牌告匯率網址：https://rate.bot.com.tw/xrt?Lang=zh-TW
再來點選
html 打開設定，Select 的地方填入 .rate-content-cash.text-right.print_hide ，注意這邊的 Select 是 CSS 選擇器，就跟我們在寫 CSS 是一樣，例如我們要抓取的 class 在 HTML 呈現是 class=”rate-content-cash text-right print_hide”，選擇器就變成 .rate-content-cash.text-right.print_hide。
Output 選擇
the html content 或 only the text content 都可以，設定好之後可以賦予這個標籤一個名稱，我這邊給它命名為 Select_Filter。
這時候我們先不要急著設定
function 內容，先把這個流程 Deploy，點選 inject 看一下結果會是怎樣，結果呈現一組陣列，這組陣列表示整份網頁裡面 .rate-content-cash.text-right.print_hide 的值依序排列，而我們要的日幣匯率就在劃線的地方，這邊可能就要手動數一下，日幣匯率是排在陣列的第幾個位置，這邊我算出來是在第 15 與 16 位，對應到陣列就是 14 和 15 ( 陣列第一個位置為 0 開始算 )，而第一個日幣匯率是銀行買入的不用看，要買日幣就要看第二個銀行賣出，也就是第 15 位。
function 打開設定，輸入下面這段程式碼，最後顯示的結果就會是「( 時:分:秒 ) 日幣匯率：....」。
var jp = msg.payload[15];
var date = new Date();
var h = date.getHours();
var m = date.getMinutes();
var s = date.getSeconds();
if(h<10){
h = '0'+h;
}
if(m<10){
m = '0' + m;
}
if(s<10){
s = '0' + s;
}
msg.payload = '(' + h + ':' + m + ':' + s + ')\n'+
'日幣匯率：' + jp ;
msg.rate = jp;
if(jp<0.30){
msg.jp29 = 'on' ;
}else{
msg.jp29 = 'off' ;
}
return msg;
接著點選
function 打開設定，輸入下面這段程式碼var jp = msg.payload[15];
msg.rate = jp;
if(jp<0.30){
msg.payload = 'on' ;
}else{
msg.payload = 'off' ;
}
return msg;
設定 匯率 < 0.30 ON 否則 OFF (0.30 或是其他數值 控制On/Off)
設定MQTT server 配合ESP8266 NodeMCU u'P 控制LED ON /LED OFF
(JPY) 這個
function 節點，這邊就純粹針對匯率做判斷，如果小於多少就傳出 on，不然就傳出 off。 if(jp<0.30){
msg.jp29 = 'on' ;
}else{
msg.jp29 = 'off' ;
var jp = msg.payload[15]; var date = new Date(); var h = date.getHours(); var m = date.getMinutes(); var s = date.getSeconds(); if(h<10){ h = '0'+h; } if(m<10){ m = '0' + m; } if(s<10){ s = '0' + s; } msg.payload = '(' + h + ':' + m + ':' + s + ')\n'+ '日幣匯率：' + jp ; msg.rate = jp; if(jp<0.30){ msg.jp29 = 'on' ; }else{ msg.jp29 = 'off' ; } return msg;
switch 的流程，目的在於判斷如果是 on 就走寄信的流程，如果是 off 則顯示訊息就好。
接著 set mail 這個
function 節點，
接著 send gmail 這個var jp = msg.rate;var date = new Date();var h = date.getHours();var m = date.getMinutes();var s = date.getSeconds();if(h<10){h = '0'+h;}if(m<10){m = '0' + m;}if(s<10){s = '0' + s;}msg.to = 'alex.pts2594@gmail.com';msg.topic = '該買日幣囉！('+jp+')';msg.payload = '(' + h + ':' + m + ':' + s + ') '+'日幣匯率：' + jp ;return msg;
email 節點，
Depoly 之後點選
inject 啟動，可以設定每一分鐘或每兩分鐘抓取一次匯率，當匯率到達一定數值的時候，就會自動寄發 Email 並且點亮LED燈泡囉！
另外利用MQTT in 檢視送出的資料是否正確或是ESP8266 NodeMcu 回送的資料是否正確
Node-RED 送出on , off 可以利用ESP8266 NodeMcu 程式 回傳A , B 或是0 ,1 信號
設定MQTT IN
再來設定顯示畫面
[{"id":"75d62350.b6310c","type":"mqtt out","z":"17bb63ed.68b25c","name":"JP Rate","topic":"alex9ufo/Jprate","qos":"0","retain":"true","broker":"b0f7c1ff.aede5","x":700,"y":340,"wires":[]},{"id":"dd75c89f.246658","type":"inject","z":"17bb63ed.68b25c","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":100,"y":280,"wires":[["b984576b.3db788"]]},{"id":"b984576b.3db788","type":"http request","z":"17bb63ed.68b25c","name":"","method":"GET","ret":"txt","url":"https://rate.bot.com.tw/xrt?Lang=zh-TW","tls":"","x":250,"y":280,"wires":[["a586a73d.e7e968"]]},{"id":"742c5861.77e038","type":"function","z":"17bb63ed.68b25c","name":"(JPY) ","func":"var jp = msg.payload[15];\nvar date = new Date();\nvar h = date.getHours();\nvar m = date.getMinutes();\nvar s = date.getSeconds();\nif(h<10){\n h = '0'+h;\n}\nif(m<10){\n m = '0' + m;\n}\nif(s<10){\n s = '0' + s;\n}\nmsg.payload = '(' + h + ':' + m + ':' + s + ')\\n'+\n'日幣匯率：' + jp ;\n\nmsg.rate = jp;\nif(jp<0.30){\n msg.jp29 = 'on' ;\n}else{\n msg.jp29 = 'off' ;\n}\n\nreturn msg;\n","outputs":1,"noerr":0,"x":190,"y":440,"wires":[["2647bcb6.04b4f4","88d5c709.ef2d48"]]},{"id":"85a49c7e.8c917","type":"e-mail","z":"17bb63ed.68b25c","server":"smtp.gmail.com","port":"465","secure":true,"name":"alex.pts2594@gmail.com","dname":"send gmail","x":690,"y":400,"wires":[]},{"id":"4fe101eb.f32a6","type":"function","z":"17bb63ed.68b25c","name":"set mail","func":"var jp = msg.rate;\nvar date = new Date();\nvar h = date.getHours();\nvar m = date.getMinutes();\nvar s = date.getSeconds();\nif(h<10){\n h = '0'+h;\n}\nif(m<10){\n m = '0' + m;\n}\nif(s<10){\n s = '0' + s;\n}\nmsg.to = 'alex.pts2594@gmail.com';\nmsg.topic = '該買日幣囉！('+jp+')';\nmsg.payload = '(' + h + ':' + m + ':' + s + ') '+\n'日幣匯率：' + jp ;\nreturn msg;","outputs":1,"noerr":0,"x":540,"y":420,"wires":[["85a49c7e.8c917","5883fca3.223114"]]},{"id":"bd11d496.74e128","type":"debug","z":"17bb63ed.68b25c","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":690,"y":480,"wires":[]},{"id":"88d5c709.ef2d48","type":"switch","z":"17bb63ed.68b25c","name":"","property":"jp29","propertyType":"msg","rules":[{"t":"eq","v":"on","vt":"str"},{"t":"neq","v":"on","vt":"str"}],"checkall":"true","repair":false,"outputs":2,"x":370,"y":440,"wires":[["4fe101eb.f32a6"],["bd11d496.74e128"]]},{"id":"a586a73d.e7e968","type":"html","z":"17bb63ed.68b25c","name":"Select_Filter","property":"payload","tag":".rate-content-cash.text-right.print_hide","ret":"html","as":"single","x":210,"y":360,"wires":[["742c5861.77e038","1d4ce786.7df658","60b8b7b5.42b3a8"]]},{"id":"990be0ca.6ac98","type":"mqtt in","z":"17bb63ed.68b25c","name":"Jp Rate","topic":"alex9ufo/Jprate","qos":"2","broker":"b0f7c1ff.aede5","x":70,"y":540,"wires":[["802395c2.98fff8","af2c3d09.0421c","fc81fb8.f3b5108"]]},{"id":"af2c3d09.0421c","type":"debug","z":"17bb63ed.68b25c","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":270,"y":580,"wires":[]},{"id":"802395c2.98fff8","type":"ui_switch","z":"17bb63ed.68b25c","name":"","label":"switch","group":"68a79aa3.bcb534","order":0,"width":0,"height":0,"passthru":true,"decouple":"false","topic":"","style":"","onvalue":"on","onvalueType":"str","onicon":"","oncolor":"","offvalue":"off","offvalueType":"str","officon":"","offcolor":"","x":250,"y":540,"wires":[[]]},{"id":"5883fca3.223114","type":"debug","z":"17bb63ed.68b25c","name":"","active":false,"tosidebar":false,"console":false,"tostatus":false,"complete":"payload","x":690,"y":440,"wires":[]},{"id":"1d4ce786.7df658","type":"debug","z":"17bb63ed.68b25c","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":490,"y":280,"wires":[]},{"id":"2647bcb6.04b4f4","type":"debug","z":"17bb63ed.68b25c","name":"","active":true,"tosidebar":false,"console":false,"tostatus":false,"complete":"jp29","x":380,"y":500,"wires":[]},{"id":"60b8b7b5.42b3a8","type":"function","z":"17bb63ed.68b25c","name":"(JPY) on off","func":"var jp = msg.payload[15];\nmsg.rate = jp;\nif(jp<0.29){\n msg.payload = 'on' ;\n}else{\n msg.payload = 'off' ;\n}\nreturn msg;","outputs":1,"noerr":0,"x":490,"y":340,"wires":[["75d62350.b6310c"]]},{"id":"fc81fb8.f3b5108","type":"ui_text","z":"17bb63ed.68b25c","group":"68a79aa3.bcb534","order":0,"width":0,"height":0,"name":"","label":"text","format":"{{msg.payload}}","layout":"row-spread","x":250,"y":620,"wires":[]},{"id":"b0f7c1ff.aede5","type":"mqtt-broker","z":"","name":"mqtt","broker":"broker.mqtt-dashboard.com","port":"1883","clientid":"","usetls":false,"compatmode":true,"keepalive":"60","cleansession":true,"willTopic":"","willQos":"0","willPayload":"","birthTopic":"","birthQos":"0","birthRetain":"true","birthPayload":""},{"id":"68a79aa3.bcb534","type":"ui_group","z":"","name":"alexJp_Rate","tab":"a0a49c3.906956","order":1,"disp":true,"width":"6","collapse":false},{"id":"a0a49c3.906956","type":"ui_tab","z":"","name":"alex9ufo JP Rate","icon":"dashboard"}]
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