d3.formatSpecifier()

d3.formatSpecifier(specifier)

Parses the specified specifier, returning an object with exposed fields that correspond to the format specification mini-language and a toString method that reconstructs the specifier. For example, formatSpecifier("s") returns:

{
  "fill": " ",
  "align": ">",
  "sign": "-",
  "symbol": "",
  "zero": false,
  "width": undefined,
  "comma": false,
  "precision": 6,
  "type": "s"
}

This method is useful for understanding how format specifiers are parsed and for deriving new specifiers. For example, you might compute an appropriate precision based on the numbers you want to format using precisionFixed and then create a new format:

var s = d3.formatSpecifier("f");
s.precision = precisionFixed(0.01);
var f = d3.format(s);
f(42); // "42.00";