Avoid using Function constructor.

[vrana]

Using the Function constructor is not compatible with CSP without
'unsafe-eval' as it evals the passed code. Use a function literal
instead.

[mbostock]

This behavior is noted in the README along with the suggestion to use parseRows if a CSP is in place. Changing the implementation as proposed here had a substantial negative performance impact, at least last time I measured it, and so I am wary of changing the default behavior. If you want to verify that this behavior has been fixed in modern browsers for large input files, then I will reconsider this request. Thank you!

[vrana]

Please give me instructions about how you want to measure this.

[vrana]

I was able to reproduce the slowness in Chrome by parsing Appearances.csv from http://seanlahman.com/baseball-archive/statistics/. I'll debug what's going on and update this pull request with a faster version.

Browser	Old code	New Code
Chrome 58	376 ms	1462 ms

[vrana]

I was able to bring it down with this code:

function objectConverter(columns) {
  var result = {};
  return function(d) {
    for (var i = 0; i < columns.length; i++) {
      result[columns[i]] = d[i];
    }
    return result;
  };
}

Browser	Old code	New Code
Chrome 58 Linux	376 ms	539 ms
Firefox 53 Linux	941 ms	725 ms

It's slightly faster in Firefox and slightly slower in Chrome. Is this acceptable for you?

I've also updated the README which should appear if you re-open this pull request.

[mbostock]

That implementation returns the same object for every row rather than a new object for each row.

[vrana]

You are right.

[vrana]

I will not be able to make this fast. Thanks for your feedback.

[vrana]

This is still biting us. People keep using this function and when we want to deploy CSP, we need to refactor. Would you accept a patch using the CSP-compatible version if CSP is enabled? I can use a try-catch around the Function constructor.

This is a benchmark from today:

Code	Chrome 94
Original	0.026 ms
try-catch with CSP disabled	0.026 ms
try-catch with CSP enabled	0.098 ms

Also, this is so quick these days that maybe it's not worth optimizing anymore?

[vrana]

Created #87.

[vrana]

This is the original benchmark with this code:

function objectConverter(columns) {
  return function(d) {
    var result = {};
    for (var i = 0; i < columns.length; i++) {
      result[columns[i]] = d[i] || '';
    }
    return result;
  };
}

Browser	Original	CSP compatible
Chrome 94	178 ms	371 ms
Firefox 78	445 ms	647 ms