Task: Track changes of product prices

n8n workflow:
{"nodes":[{"name":"HTML Extract","type":"n8n-nodes-base.htmlExtract","position":[-220,-390],"parameters":{"options":{},"extractionValues":{"values":[{"key":"price","cssSelector":"={{$node[\"initItem\"].json[\"selector\"]}}"}]}},"typeVersion":1},{"name":"Cron","type":"n8n-nodes-base.cron","position":[-1290,-390],"parameters":{"triggerTimes":{"item":[{"mode":"everyX","unit":"minutes","value":15}]}},"typeVersion":1},{"name":"getActualPrice","type":"n8n-nodes-base.functionItem","position":[-20,-390],"parameters":{"functionCode":"const globalData = getWorkflowStaticData('global');\n\nvar price = String(item.price).replace(\",\", \".\");\nprice = parseFloat(price);\n//price = price.replace(/\\D/g, '');\n//item.price = String(item.price).replace(\",\", \".\");\n//item.price = parseFloat(item.price);\n\nitem.priceExists = (price > 0 ? true : false)\nitem.price = price;\n\n// Update its data\nglobalData.actualPrice = item;\n\nreturn item;"},"typeVersion":1},{"name":"fetchWeb","type":"n8n-nodes-base.httpRequest","position":[-410,-390],"parameters":{"url":"={{$node[\"initItem\"].json[\"link\"]}}","options":{},"responseFormat":"string"},"typeVersion":1},{"name":"FunctionItem","type":"n8n-nodes-base.functionItem","position":[1020,-390],"parameters":{"functionCode":"const globalData = getWorkflowStaticData('global');\n\nglobalData.iteration = 0;\n//var thiselem = $node[\"initItem\"].json;\n\n//const s1 = {'slug': thiselem.slug, \"link\": thiselem.link, \"selector\": thiselem.selector, \"price\":$node[\"getActualPrice\"].json.price, \"currency\": thiselem.currency};\n//const s2 = {'slug': thiselem.slug+'2', \"link\": thiselem.link, \"selector\": thiselem.selector, \"price\":$node[\"getActualPrice\"].json.price, \"currency\": thiselem.currency};\n//const s3 = {'slug': thiselem.slug+'3', \"link\": thiselem.link, \"selector\": thiselem.selector, \"price\":$node[\"getActualPrice\"].json.price, \"currency\": thiselem.currency};\n\nreturn $node[\"changeME\"].json.myWatchers;\n"},"typeVersion":1},{"name":"Write Binary File1","type":"n8n-nodes-base.writeBinaryFile","position":[1850,-390],"parameters":{"fileName":"/data/kopacky.json","dataPropertyName":"=price"},"typeVersion":1},{"name":"Move Binary Data1","type":"n8n-nodes-base.moveBinaryData","position":[1420,-390],"parameters":{"mode":"jsonToBinary","options":{},"destinationKey":"price"},"typeVersion":1},{"name":"IF1","type":"n8n-nodes-base.if","position":[550,-370],"parameters":{"conditions":{"string":[{"value1":"={{$node[\"checkifexists\"].json[\"stdout\"]}}","value2":"Exists","operation":"notEqual"}]}},"typeVersion":1},{"name":"checkifexists","type":"n8n-nodes-base.executeCommand","position":[410,-370],"parameters":{"command":"if [ -r /data/kopacky.json ]; then echo Exists; fi"},"typeVersion":1},{"name":"IF3","type":"n8n-nodes-base.if","position":[680,110],"parameters":{"conditions":{"string":[{"value1":"={{$node[\"checkifexists\"].json[\"stdout\"]}}","value2":"Exists"}]}},"typeVersion":1},{"name":"SaveToFile","type":"n8n-nodes-base.writeBinaryFile","position":[1650,110],"parameters":{"fileName":"/data/kopacky.json","dataPropertyName":"=price"},"typeVersion":1},{"name":"JsonToBinary","type":"n8n-nodes-base.moveBinaryData","position":[1500,110],"parameters":{"mode":"jsonToBinary","options":{},"destinationKey":"price"},"typeVersion":1},{"name":"changeME","type":"n8n-nodes-base.functionItem","color":"#3BDD33","position":[-830,-390],"parameters":{"functionCode":"const globalData = getWorkflowStaticData('global');\n\n//{'slug': 'kopacky', 'link': 'https://www.adsport.sk/kopacky-lisovky-adidas-x-19-3-ll-fg-ef0598/#1131861', 'currency': 'EUR'}[]\nvar myWatchers = [\n{'slug': 'kopacky', 'link': 'https://www.adsport.sk/kopacky-lisovky-adidas-x-19-3-ll-fg-ef0598/#1131861', 'selector':'.prices > strong:nth-child(1) > span:nth-child(1)', 'currency': 'EUR'},\n{'slug': 'kopacky2', 'link': 'https://www.adsport.sk/turfy-adidas-ace-tango-17-3-tf-by2203/', 'selector':'.col-xs-4 > strong:nth-child(1) > span:nth-child(1)', 'currency': 'EUR'},\n{'slug': 'mobilcek', 'link': 'https://mobil.bazos.sk/inzerat/112253662/predam-odolny-doogee-s60-52-4g-lte-nfc.php', 'selector':'.listadvlevo > table:nth-child(1) > tbody:nth-child(1) > tr:nth-child(5) > td:nth-child(2) > b:nth-child(2)', 'currency': 'EUR'},\n{'slug': 'ADIZERO RC 2', 'link': 'https://www.adsport.sk/panske-bezecke-topanky-adidas-adizero-rc-2-eg1187/', 'selector':'.col-xs-4 > strong:nth-child(1) > span:nth-child(1)', 'currency': 'EUR'}\n];\n\nitem.myWatchers = myWatchers;\nitem.watchersCount = myWatchers.length;\nglobalData.myWatchers = myWatchers;\n\nreturn item;"},"typeVersion":1},{"name":"initItem","type":"n8n-nodes-base.functionItem","position":[-620,-390],"parameters":{"functionCode":"const globalData = getWorkflowStaticData('global');\n\nvar counter = globalData.iteration;\n\nitem.myWatchers[counter].watchersCount = item.watchersCount;\nitem.myWatchers[counter].canContinue = (globalData.iteration < item.watchersCount-1 ? true : false);\n//item.myWatchers[counter].canContinue = false;\n\nglobalData.iteration = counter + 1;\n\nreturn item.myWatchers[counter];"},"typeVersion":1},{"name":"savedItems","type":"n8n-nodes-base.readBinaryFile","position":[850,-20],"parameters":{"filePath":"/data/kopacky.json","dataPropertyName":"savedItems"},"typeVersion":1,"continueOnFail":true,"alwaysOutputData":true},{"name":"itemsToJSON","type":"n8n-nodes-base.moveBinaryData","position":[1020,-20],"parameters":{"options":{},"sourceKey":"savedItems"},"typeVersion":1},{"name":"IF","type":"n8n-nodes-base.if","position":[2190,-90],"parameters":{"conditions":{"string":[],"boolean":[{"value1":"={{$node[\"initItem\"].json[\"canContinue\"]}}","value2":true}]}},"typeVersion":1},{"name":"initItem1","type":"n8n-nodes-base.functionItem","position":[-1060,-390],"parameters":{"functionCode":"const globalData = getWorkflowStaticData('global');\n\nglobalData.iteration = 0;\n\nreturn item;"},"typeVersion":1},{"name":"IF2","type":"n8n-nodes-base.if","position":[1850,110],"parameters":{"conditions":{"number":[{"value1":"={{$node[\"getActualPrice\"].json[\"price\"]}}","value2":"={{$node[\"updateSavedItems1\"].json[\"oldPrice\"]}}"}],"string":[]}},"typeVersion":1},{"name":"updateSavedItems","type":"n8n-nodes-base.functionItem","position":[1350,110],"parameters":{"functionCode":"const globalData = getWorkflowStaticData('global');\n\nvar myitems = [];\nvar i;\nfor (i = 0; i < item.items.length; i++) { \n  if($node[\"initItem\"].json.slug == item.items[i].slug && $node[\"getActualPrice\"].json.price < item.items[i].price) {\n    item.items[i].price = $node[\"getActualPrice\"].json.price;\n  }\n  myitems.push(item.items[i]);\n} \n\nreturn myitems;\n"},"typeVersion":1},{"name":"updateSavedItems1","type":"n8n-nodes-base.functionItem","position":[1200,-20],"parameters":{"functionCode":"const globalData = getWorkflowStaticData('global');\nvar oldPrice = null;\nvar myitems = [];\nvar i;\nfor (i = 0; i < item.length; i++) {\n  if($node[\"initItem\"].json.slug == item[i].slug) {\n\n    item[i].link = $node[\"initItem\"].json.link;\n    item[i].selector = $node[\"initItem\"].json.selector;\n    item[i].currency = $node[\"initItem\"].json.currency;\n    \n    if(!item[i].price){\n      item[i].price = $node[\"getActualPrice\"].json.price;\n    }\n    \n    if($node[\"getActualPrice\"].json.price < item[i].price){\n      oldPrice = item[i].price;\n      item[i].price = $node[\"getActualPrice\"].json.price;\n    }\n    \n    \n  }\n  \n  myitems.push(item[i]);\n} \n\n//item.somar = $node[\"initItem\"].json;\n//return globalData.actualPrice;\n\nvar itemm = {};\nitemm.items = myitems;\nitemm.oldPrice = oldPrice;\nreturn itemm;\n"},"typeVersion":1},{"name":"cleanData","type":"n8n-nodes-base.executeCommand","notes":"This will remove all storaged data.","position":[-1290,-560],"parameters":{"command":"file=\"/data/kopacky.json\"\n[ -f $file ] && rm $file"},"typeVersion":1},{"name":"IF4","type":"n8n-nodes-base.if","position":[150,-390],"parameters":{"conditions":{"string":[],"boolean":[{"value1":"={{$node[\"getActualPrice\"].json[\"priceExists\"]}}"}]}},"typeVersion":1},{"name":"NotifyBetterPrice","type":"n8n-nodes-base.emailSend","position":[1850,-90],"parameters":{"html":"=<h2>Nová cena je: {{$node[\"getActualPrice\"].json[\"price\"]}} {{$node[\"initItem\"].json[\"currency\"]}}</h2><br>\nPôvodná cena bola: {{$node[\"updateSavedItems1\"].json[\"oldPrice\"]}} {{$node[\"initItem\"].json[\"currency\"]}}<br>\nURL: {{$node[\"initItem\"].json[\"link\"]}}","text":"=","options":{},"subject":"=Nová cena - {{$node[\"initItem\"].json[\"slug\"]}} - {{$node[\"getActualPrice\"].json[\"price\"]}} {{$node[\"initItem\"].json[\"currency\"]}}","toEmail":"sthosstudio@gmail.com","fromEmail":"hostovecky@weyou.sk"},"credentials":{"smtp":"hostovecky@weyou.sk"},"typeVersion":1},{"name":"NotifyIncorrectPrice","type":"n8n-nodes-base.emailSend","position":[270,-690],"parameters":{"html":"=Please check the link or selector for the item with slug <strong>{{$node[\"initItem\"].json[\"slug\"]}}</strong><br>\nURL: {{$node[\"initItem\"].json[\"link\"]}}","text":"=","options":{},"subject":"={{$node[\"initItem\"].json[\"slug\"]}} - Getting price issue.","toEmail":"sthosstudio@gmail.com","fromEmail":"hostovecky@weyou.sk"},"credentials":{"smtp":"hostovecky@weyou.sk"},"typeVersion":1}],"connections":{"IF":{"main":[[{"node":"changeME","type":"main","index":0}]]},"IF1":{"main":[[{"node":"FunctionItem","type":"main","index":0}],[{"node":"IF3","type":"main","index":0}]]},"IF2":{"main":[[{"node":"NotifyBetterPrice","type":"main","index":0}],[{"node":"IF","type":"main","index":0}]]},"IF3":{"main":[[{"node":"savedItems","type":"main","index":0}]]},"IF4":{"main":[[{"node":"NotifyIncorrectPrice","type":"main","index":0}],[{"node":"checkifexists","type":"main","index":0}]]},"Cron":{"main":[[{"node":"initItem1","type":"main","index":0}]]},"changeME":{"main":[[{"node":"initItem","type":"main","index":0}]]},"fetchWeb":{"main":[[{"node":"HTML Extract","type":"main","index":0}]]},"initItem":{"main":[[{"node":"fetchWeb","type":"main","index":0}]]},"initItem1":{"main":[[{"node":"changeME","type":"main","index":0}]]},"SaveToFile":{"main":[[{"node":"IF2","type":"main","index":0}]]},"savedItems":{"main":[[{"node":"itemsToJSON","type":"main","index":0}]]},"itemsToJSON":{"main":[[{"node":"updateSavedItems1","type":"main","index":0}]]},"FunctionItem":{"main":[[{"node":"Move Binary Data1","type":"main","index":0}]]},"HTML Extract":{"main":[[{"node":"getActualPrice","type":"main","index":0}]]},"JsonToBinary":{"main":[[{"node":"SaveToFile","type":"main","index":0}]]},"checkifexists":{"main":[[{"node":"IF1","type":"main","index":0}]]},"getActualPrice":{"main":[[{"node":"IF4","type":"main","index":0}]]},"updateSavedItems":{"main":[[{"node":"JsonToBinary","type":"main","index":0}]]},"Move Binary Data1":{"main":[[{"node":"Write Binary File1","type":"main","index":0}]]},"NotifyBetterPrice":{"main":[[{"node":"IF","type":"main","index":0}]]},"updateSavedItems1":{"main":[[{"node":"updateSavedItems","type":"main","index":0}]]},"Write Binary File1":{"main":[[{"node":"IF","type":"main","index":0}]]},"NotifyIncorrectPrice":{"main":[[{"node":"checkifexists","type":"main","index":0}]]}}}