Cannot parse array from http request body in Node

Question

I am trying to consume an application/x-www-form-urlencoded encoded POST body in my node.js route.

Request using curl on the command line:

curl -X POST -H "Content-Type: application/x-www-form-urlencoded" -d 'trx[0][trx_amt]=4166481.208338&trx[0][trx_crdr]=CR&trx[0][trx_tran_type]=TR&trx[0][trx_ref1]=5979NY270557&trx[1][trx_amt]=-5735967.281740&trx[1][trx_crdr]=DR&trx[1][trx_tran_type]=II&trx[1][trx_ref1]=7305XN175748' localhost:8080/api/test

I now want to parse those values and put them into an array of arrays (no key/value pairs). Parsing the values from the request body works fine, putting them into an array as well (current_trx), but pushing that array as an element into another array (trx_data) leaves the array blank. Please help me understand what the problem is.

app.post("/api/test", (req, res) => {
 
  console.log(JSON.stringify(req.headers));
  console.log(req.body);

  var trx_data = [];
  var current_trx = [];

  for (let i = 0; i < req.body.trx.length; i++) {
    current_trx.push(parseFloat(req.body.trx[i].trx_amt));
    current_trx.push(req.body.trx[i].trx_crdr);
    current_trx.push(req.body.trx[i].trx_tran_type);
    current_trx.push(req.body.trx[i].trx_ref1);
    
    trx_data.push(current_trx); // this seems not to have any effect, trx_data remains empty
    
    console.log("CURRENT_TRX:");
    console.log(current_trx);  // this works fine, output as expected

    // emptying current_trx for the next loop
    while (current_trx.length > 0) {
      current_trx.pop();
    }
  }

  console.log("TRX_DATA ARRAY");  // empty..
  console.log(trx_data);

  res.sendStatus(200);

});

Rahul Sharma · Accepted Answer · 2022-01-03 12:38:11Z

1

You can use Array.map to solve this,

You are adding values to trx_data and emptying the same. you can move var current_trx = []; inside loop, which will also solve the issue is removed clearing logic.

app.post("/api/test", (req, res) => {
  const trx = req.body.trx;
  const trx_data = trx.map((item) => {
    const current_trx = [];
    current_trx.push(parseFloat(item.trx_amt));
    current_trx.push(item.trx_crdr);
    current_trx.push(item.trx_tran_type);
    current_trx.push(item.trx_ref1);
    return current_trx;
  });
  console.log(trx_data);
  res.sendStatus(200);
});

answered Jan 3, 2022 at 12:38

Rahul Sharma

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1 Comment

Siedler Over a year ago

Thank you. Moving var current_trx = [] inside the loop and removing the pop function solved the problem. However, I don't understand why.. current_trx is populated in each loop, then pushed to trx_data and then the content of current_trxis removed, not the content of trx_data. Hence I am not sure why the trx_data is empty.. I haven't removed any values from it.

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