src/locale/number-format.js

import "../arrays/map";
import "../core/identity";
import "../format/formatPrefix";
import "../format/precision";
import "../format/round";

function d3_locale_numberFormat(locale) {
  var locale_decimal = locale.decimal,
      locale_thousands = locale.thousands,
      locale_grouping = locale.grouping,
      locale_currency = locale.currency,
      formatGroup = locale_grouping ? function(value) {
        var i = value.length,
            t = [],
            j = 0,
            g = locale_grouping[0];
        while (i > 0 && g > 0) {
          t.push(value.substring(i -= g, i + g));
          g = locale_grouping[j = (j + 1) % locale_grouping.length];
        }
        return t.reverse().join(locale_thousands);
      } : d3_identity;

  return function(specifier) {
    var match = d3_format_re.exec(specifier),
        fill = match[1] || " ",
        align = match[2] || ">",
        sign = match[3] || "",
        symbol = match[4] || "",
        zfill = match[5],
        width = +match[6],
        comma = match[7],
        precision = match[8],
        type = match[9],
        scale = 1,
        prefix = "",
        suffix = "",
        integer = false;

    if (precision) precision = +precision.substring(1);

    if (zfill || fill === "0" && align === "=") {
      zfill = fill = "0";
      align = "=";
      if (comma) width -= Math.floor((width - 1) / 4);
    }

    switch (type) {
      case "n": comma = true; type = "g"; break;
      case "%": scale = 100; suffix = "%"; type = "f"; break;
      case "p": scale = 100; suffix = "%"; type = "r"; break;
      case "b":
      case "o":
      case "x":
      case "X": if (symbol === "#") prefix = "0" + type.toLowerCase();
      case "c":
      case "d": integer = true; precision = 0; break;
      case "s": scale = -1; type = "r"; break;
    }

    if (symbol === "$") prefix = locale_currency[0], suffix = locale_currency[1];

    // If no precision is specified for r, fallback to general notation.
    if (type == "r" && !precision) type = "g";

    // Ensure that the requested precision is in the supported range.
    if (precision != null) {
      if (type == "g") precision = Math.max(1, Math.min(21, precision));
      else if (type == "e" || type == "f") precision = Math.max(0, Math.min(20, precision));
    }

    type = d3_format_types.get(type) || d3_format_typeDefault;

    var zcomma = zfill && comma;

    return function(value) {
      var fullSuffix = suffix;

      // Return the empty string for floats formatted as ints.
      if (integer && (value % 1)) return "";

      // Convert negative to positive, and record the sign prefix.
      var negative = value < 0 || value === 0 && 1 / value < 0 ? (value = -value, "-") : sign;

      // Apply the scale, computing it from the value's exponent for si format.
      // Preserve the existing suffix, if any, such as the currency symbol.
      if (scale < 0) {
        var unit = d3.formatPrefix(value, precision);
        value = unit.scale(value);
        fullSuffix = unit.symbol + suffix;
      } else {
        value *= scale;
      }

      // Convert to the desired precision.
      value = type(value, precision);

      // Break the value into the integer part (before) and decimal part (after).
      var i = value.lastIndexOf("."),
          before = i < 0 ? value : value.substring(0, i),
          after = i < 0 ? "" : locale_decimal + value.substring(i + 1);

       // If the fill character is not "0", grouping is applied before padding.
      if (!zfill && comma) before = formatGroup(before);

      var length = prefix.length + before.length + after.length + (zcomma ? 0 : negative.length),
          padding = length < width ? new Array(length = width - length + 1).join(fill) : "";

      // If the fill character is "0", grouping is applied after padding.
      if (zcomma) before = formatGroup(padding + before);

      // Apply prefix.
      negative += prefix;

      // Rejoin integer and decimal parts.
      value = before + after;

      return (align === "<" ? negative + value + padding
            : align === ">" ? padding + negative + value
            : align === "^" ? padding.substring(0, length >>= 1) + negative + value + padding.substring(length)
            : negative + (zcomma ? value : padding + value)) + fullSuffix;
    };
  };
}

// [[fill]align][sign][symbol][0][width][,][.precision][type]
var d3_format_re = /(?:([^{])?([<>=^]))?([+\- ])?([$#])?(0)?(\d+)?(,)?(\.-?\d+)?([a-z%])?/i;

var d3_format_types = d3.map({
  b: function(x) { return x.toString(2); },
  c: function(x) { return String.fromCharCode(x); },
  o: function(x) { return x.toString(8); },
  x: function(x) { return x.toString(16); },
  X: function(x) { return x.toString(16).toUpperCase(); },
  g: function(x, p) { return x.toPrecision(p); },
  e: function(x, p) { return x.toExponential(p); },
  f: function(x, p) { return x.toFixed(p); },
  r: function(x, p) { return (x = d3.round(x, d3_format_precision(x, p))).toFixed(Math.max(0, Math.min(20, d3_format_precision(x * (1 + 1e-15), p)))); }
});

function d3_format_typeDefault(x) {
  return x + "";
}