What could be causing push() to malfunction within a loop?

Here is a snippet of my code:

var cdata = [];
  
d3.text("tests.info", function(text) {
  var data = d3.csv.parseRows(text);
  data.forEach(function(d) {
    cdata.push({key: d[0], values: []});
  });
});

The code reads a CSV file, loops through each line, and adds them into an array. I have confirmed that the data is being added correctly.

However, the problem arises when trying to access the array later on - it appears empty as if no data was ever added (even though I know this isn't the case).

I suspect it could be related to scoping, although I initially thought that push() should work in this context regardless.

Answer №1

One way to test whether cdata is empty is by utilizing a timeout function with console.log, or creating a button that reveals its content. This will demonstrate that the data is indeed present. As explained by Pointy, the following sequence of events occurs:

  • cdata is declared

  • The loading of test.info begins

  • The content of cdata is displayed

  • test.info finishes loading, triggering the initiation of data storage in your array

Answer №2

To obtain the desired result, you must retrieve the cdata:

d3.text("tests.info", function(text) {
  var data = d3.csv.parseRows(text), cdata = [];
  data.forEach(function(d) {
    cdata.push({key: d[0],values: []};
  });
  return cdata;
});

Another option to consider is simply:

d3.text("tests.info", function(text) {
  return d3.csv.parseRows(text).map(function(d) {
    return {key: d[0], values: []};
  });
});

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