Task: Sum or aggregate a column of spreadsheet or table data

n8n workflow JSON:
{"nodes":[{"name":"On clicking 'execute'","type":"n8n-nodes-base.manualTrigger","position":[220,80],"parameters":{},"typeVersion":1},{"name":"Mock data","type":"n8n-nodes-base.function","position":[420,80],"parameters":{"functionCode":"// Code here will run only once, no matter how many input items there are.\n// More info and help: https://docs.n8n.io/nodes/n8n-nodes-base.function\n\n\nreturn [ { json: { amount_USD: 50 } }, { json: { amount_USD: 20 } }, { json: { amount_USD: 60 } } ];"},"typeVersion":1},{"name":"Summing function","type":"n8n-nodes-base.function","position":[660,80],"parameters":{"functionCode":"// Code here will run only once, no matter how many input items there are.\n// More info and help: https://docs.n8n.io/nodes/n8n-nodes-base.function\n\n//Setup an empty variable to hold the count\nlet total = 0;\n\n//Loop over the incoming items of data\nfor (item of items) {\n  //For each item of data, add the amount_USD to our total counter\n  total += item.json.amount_USD;\n}\n\n//Returns a well formed JSON object with just the total_value . You can either add more data to this returned object OR use the set node afterwards to do it in a no-code way.\nreturn [ { json: { total_value: total } } ];"},"typeVersion":1}],"connections":{"Mock data":{"main":[[{"node":"Summing function","type":"main","index":0}]]},"On clicking 'execute'":{"main":[[{"node":"Mock data","type":"main","index":0}]]}}}