d3/_site/src/core/format.js

A small, free JavaScript library for manipulating documents based on data.

// TODO align, type
d3.format = function(specifier) {
  var match = d3_format_re.exec(specifier),
      fill = match[1] || " ",
      sign = match[3] || "",
      zfill = match[5],
      width = +match[6],
      comma = match[7],
      precision = match[8],
      type = match[9];
  if (precision) precision = precision.substring(1);
  if (zfill) {
    fill = "0"; // TODO align = "=";
    if (comma) width -= Math.floor((width - 1) / 4);
  }
  if (type == "d") precision = "0";
  return function(value) {
    var number = +value,
        negative = (number < 0) && (number = -number) ? "\u2212" : sign;

    // Return the empty string for floats formatted as ints.
    if ((type == "d") && (number % 1)) return "";

    // Convert the input value to the desired precision.
    if (precision) value = number.toFixed(precision);
    else value = "" + number;

    // If the fill character is 0, the sign and group is applied after the fill.
    if (zfill) {
      var length = value.length + negative.length;
      if (length < width) value = new Array(width - length + 1).join(fill) + value;
      if (comma) value = d3_format_group(value);
      value = negative + value;
    }

    // Otherwise (e.g., space-filling), the sign and group is applied before.
    else {
      if (comma) value = d3_format_group(value);
      value = negative + value;
      var length = value.length;
      if (length < width) value = new Array(width - length + 1).join(fill) + value;
    }

    return value;
  };
};

// [[fill]align][sign][#][0][width][,][.precision][type]
var d3_format_re = /(?:([^{])?([<>=^]))?([+\- ])?(#)?(0)?([0-9]+)?(,)?(\.[0-9]+)?([a-zA-Z%])?/;

// Apply comma grouping for thousands.
function d3_format_group(value) {
  var i = value.lastIndexOf("."),
      f = i >= 0 ? value.substring(i) : (i = value.length, ""),
      t = [];
  while (i > 0) t.push(value.substring(i -= 3, i + 3));
  return t.reverse().join(",") + f;
}