JS/TS func to Dart func

Tony Hart 0
Viewed 29

I want to convert it to dart code but I dnt understand ternary operator in that code

const getPagination = (page, size) => {
  const limit = size ? +size : 3
  const from = page ? page * limit : 0
  const to = page ? from + size - 1 : size - 1

  return { from, to }
}

if you can tell me what code do line by line ??

dart javascript
2 Answers

A more idiomatic Dart implementation of the same code could be:

Range getPagination([int page = 0, int size = 3]) {
  RangeError.checkNotNegative(page, "page");
  if (size <= 0) size = 3;
  var from = page * size;
  var to = from + size - 1;
  return Range(from, to);
}

class Range {
  final int from;
  final int to;
  Range(this.from, this.to);
}

This allows you to call with no arguments, but not with null as explicit argument. So don't do that.

If you omit the size, the size is 3. That's more useful than finding a limit if size is null or 0, but then use size anyway in the to computation, instead of limit.

Using a list of integers as a pair of integers is not the Dart way. I'd create a class, like here, or wait for records and use a proper (int, int) tuple.

Dart lists, and maps, are much more expensive data structures than JavaScript "objects". A small class is what corresponds to the anonymous object {from, to} in JavaScript.

lrn0

so I convert it by looking at TS play code

void main() {
  List<int> getPagination(int? page, int? size) {
  int? limit = size ?? 3;
  int? from = page != null ? page * limit : 0;
  int? to = page != null ? (from + size!) - 1 : (size! - 1);

  return [from, to];
}
  print(getPagination(0, 10));
}

and its works thx to @blex

Tony Hart0
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