sheetjs_sheetjs/ssf.md

SSF

SpreadSheet Format (SSF) is a pure-JS library to format data using ECMA-376 spreadsheet format codes.

Options

The various API functions take an opts argument which control parsing. The default options are described below:

/* Options */
var opts_fmt = {};
function fixopts(o){for(var y in opts_fmt) if(o[y]===undefined) o[y]=opts_fmt[y];}
SSF.opts = opts_fmt;

There are two commonly-recognized date code formats:

• 1900 mode (where date=0 is 1899-12-31)
• 1904 mode (where date=0 is 1904-01-01)

The difference between the the 1900 and 1904 date modes is 1462 days. Since the 1904 date mode was only default in a few Mac variants of Excel (2011 uses 1900 mode), the default is 1900 mode. Consistent with ECMA-376 the name is date1904:

opts_fmt.date1904 = 0;

The default output is a text representation (no effort to capture colors). To control the output, set the output variable:

• text: no color (default)
• html: html output using
• ansi: ansi color codes (requires colors module)

opts_fmt.output = "";

There are a few places where the specification is ambiguous or where Excel does not follow the spec. They are noted in the document.

The mode option controls compatibility:

• ssf: options that the author believes makes the most sense (default)
• ecma: compatibility with ECMA-376
• excel: compatibility with MS-XLSX

opts_fmt.mode = "";

Conditional Format Codes

The specification is a bit unclear here. It initially claims in §18.3.1:

Up to four sections of format codes can be specified. The format codes, separated by semicolons, define the formats for positive numbers, negative numbers, zero values, and text, in that order.

Semicolons can be escaped with the \ character, so we need to split on those semicolons that aren't prefaced by a slash or within a quoted string:

function split_fmt(fmt) {
  var out = [];
  var in_str = -1;
  for(var i = 0, j = 0; i < fmt.length; ++i) {
    if(in_str != -1) { if(fmt[i] == '"') in_str = -1; continue; }
    if(fmt[i] == "_" || fmt[i] == "*" || fmt[i] == "\\") { ++i; continue; }
    if(fmt[i] == '"') { in_str = i; continue; }
    if(fmt[i] != ";") continue;
    out.push(fmt.slice(j,i));
    j = i+1;
  }
  out.push(fmt.slice(j));
  if(in_str !=-1) throw "Format |" + fmt + "| unterminated string at " + in_str;
  return out;
}
SSF._split = split_fmt;

But it also allows for conditional formatting:

To set number formats that are applied only if a number meets a specified condition, enclose the condition in square brackets. The condition consists of a comparison operator and a value. Comparison operators include: = Equal to; > Greater than; < Less than; >= Greater than or equal to, <= Less than or equal to, and <> Not equal to.

One problem is that Excel doesn't support three conditionals. For example:

[Red][<-25]General;[Blue][>25]General;[Green][<>0]General;[Yellow]General

One would expect that the format code would color all numbers that are < -25 in red, all numbers > 25 in blue, nonzero numbers between -25 and 25 in green, and color 0 and text in yellow. Excel doesn't do that.

The two-conditional case works in an "expected" way if you interpret the third clause as the case for numbers that don't fit the first two:

[Red][<-25]General;[Blue][>25]General;[Green]General;[Yellow]General

will render values below -25 as Red, above 25 as Blue, Green for other numbers, and Yellow for text.

Only the text case is allowed to have the @ text sigil. Excel interprets it as the last format.

General Number Format

The 'general' format for spreadsheets (identified by format code 0) is highly context-sensitive and the implementation tries to follow the format to the best of its abilities given the knowledge.

var general_fmt = function(v) {

Booleans are serialized in upper case:

  if(typeof v === 'boolean') return v ? "TRUE" : "FALSE";

For numbers, try to display up to 11 digits of the number:

  if(typeof v === 'number') {
    return v.toString().substr(0,11);
  }

For strings, just return the text as-is:

  if(typeof v === 'string') return v;

  throw "unsupport value in General format: " + v;
};
SSF._general = general_fmt;

Implied Number Formats

These are the commonly-used formats that have a special implied code. None of the international formats are included here.

var table_fmt = {
  1:  '0',
  2:  '0.00',
  3:  '#,##0',
  4:  '#,##0.00',
  9:  '0%',
  10: '0.00%',
  11: '0.00E+00',
  12: '# ?/?',
  13: '# ??/??',

Now Excel and other formats treat code 14 as mm/dd/yy (with slashes). Given that the spec gives no internationalization considerations, erring on the side of the applications makes sense here:

  14: 'mm/dd/yy',
  15: 'd-mmm-yy',
  16: 'd-mmm',
  17: 'mmm-yy',
  18: 'h:mm AM/PM',
  19: 'h:mm:ss AM/PM',
  20: 'h:mm',
  21: 'h:mm:ss',
  22: 'm/d/yy h:mm',
  37: '#,##0 ;(#,##0)',
  38: '#,##0 ;[Red](#,##0)',
  39: '#,##0.00;(#,##0.00)',
  40: '#,##0.00;[Red](#,##0.00)',
  45: 'mm:ss',
  46: '[h]:mm:ss',
  47: 'mmss.0',
  48: '##0.0E+0',
  49: '@'
};

These test cases were manually generated in Excel 2011 [value, code, result]:

[
  [12345.6789, 0, "12345.6789"],
  [12345.6789, 1, "12346"],
  [12345.6789, 2, "12345.68"],
  [12345.6789, 3, "12,346"],
  [12345.6789, 4, "12,345.68"],
  [12345.6789, 9, "1234568%"],
  [12345.6789, 10, "1234567.89%"],
  [12345.6789, 11, "1.23E+04"],
  [12345.6789, 12, "12345 2/3"],
  [12345.6789, 13, "12345 55/81"],
  [12345.6789, 14, "10/18/33"],
  [12345.6789, 15, "18-Oct-33"],
  [12345.6789, 16, "18-Oct"],
  [12345.6789, 17, "Oct-33"],
  [12345.6789, 18, "4:17 PM"],
  [12345.6789, 19, "4:17:37 PM"],
  [12345.6789, 20, "16:17"],
  [12345.6789, 21, "16:17:37"],
  [12345.6789, 22, "10/18/33 16:17"],
  [12345.6789, 37, "12,346"],
  [12345.6789, 38, "12,346"],
  [12345.6789, 39, "12,345.68"],
  [12345.6789, 40, "12,345.68"],
  [12345.6789, 45, "17:37"],
  [12345.6789, 46, "296296:17:37"],
  [12345.6789, 47, "1737.0"],
  [12345.6789, 48, "12.3E+3"],
  [12345.6789, 49, "12345.6789"]
]

Dates and Time

The code ddd displays short day-of-week and dddd shows long day-of-week:

var days = [
  ['Sun', 'Sunday'],
  ['Mon', 'Monday'],
  ['Tue', 'Tuesday'],
  ['Wed', 'Wednesday'],
  ['Thu', 'Thursday'],
  ['Fri', 'Friday'],
  ['Sat', 'Saturday']
];

mmm shows short month, mmmm shows long month, and mmmmm shows one char:

var months = [
  ['J', 'Jan', 'January'],
  ['F', 'Feb', 'February'],
  ['M', 'Mar', 'March'],
  ['A', 'Apr', 'April'],
  ['M', 'May', 'May'],
  ['J', 'Jun', 'June'],
  ['J', 'Jul', 'July'],
  ['A', 'Aug', 'August'],
  ['S', 'Sep', 'September'],
  ['O', 'Oct', 'October'],
  ['N', 'Nov', 'November'],
  ['D', 'Dec', 'December']
];

Parsing Date and Time Codes

Most spreadsheet formats store dates and times as floating point numbers (where the integer part is a day code based on a format and the fractional part is the portion of a 24 hour day).

var parse_date_code = function parse_date_code(v,opts) {
  var date = Math.floor(v), time = Math.round(86400 * (v - date)), dow=0;
  var dout=[], out={D:date, T:time}; fixopts(opts = (opts||{}));

Excel help actually recommends treating the 1904 date codes as 1900 date codes shifted by 1462 days.

  if(opts.date1904) date += 1462;

Due to a bug in Lotus 1-2-3 which was propagated by Excel and other variants, the year 1900 is recognized as a leap year. JS has no way of representing that abomination as a Date, so the easiest way is to store the data as a tuple.

February 29, 1900 (date 60) is recognized as a Wednesday.

  if(date === 60) {dout = [1900,2,29]; dow=3;}

For the other dates, using the JS date mechanism suffices.

  else {
    if(date > 60) --date;
    /* 1 = Jan 1 1900 */
    var d = new Date(1900,0,1);
    d.setDate(d.getDate() + date - 1);
    dout = [d.getFullYear(), d.getMonth()+1,d.getDate()];
    dow = d.getDay();

Note that Excel opted to keep the day-of-week metric consistent with the extra day. In practice, that means the days before the fake leap day are off. For example, date code 55 is "Friday, February 24, 1900" when in fact it was a Saturday. The "right" thing to do is to keep the DOW consistent and just break the fact that there are two Wednesdays in that "week".

    if(opts.mode === 'excel' && date < 60) dow = (dow + 6) % 7;
  }

Because JS dates cannot represent the bad leap day, this returns an object:

  out.y = dout[0]; out.m = dout[1]; out.d = dout[2];
  out.S = time % 60; time = Math.floor(time / 60);
  out.M = time % 60; time = Math.floor(time / 60);
  out.H = time;
  out.q = dow;
  return out;
};
SSF.parse_date_code = parse_date_code;

Evaluating Number Formats

String.prototype.reverse = function() { return this.split("").reverse().join(""); }
var commaify = function(s) { return s.reverse().replace(/.../g,"$&,").reverse(); };
var write_num = function(type, fmt, val) {

Percentage values should be physically shifted:

  var mul = 0;
  fmt = fmt.replace(/%/g,function(x) { mul++; return ""; });
  if(mul !== 0) return write_num(type, fmt, val * Math.pow(10,2*mul)) + fill("%",mul);

For exponents, get the exponent and mantissa and format them separately:

  if(fmt.indexOf("E") > -1) {
    var o = val.toExponential(fmt.indexOf("E") - fmt.indexOf(".") - 1);
    if(fmt.match(/E\+00$/) && o.match(/e[+-][0-9]$/)) o = o.substr(0,o.length-1) + "0" + o[o.length-1];
    if(fmt.match(/E\-/) && o.match(/e\+/)) o = o.replace(/e\+/,"e");
    return o.replace("e","E");
  }

The default cases are hard-coded. TODO: actually parse them

  var ff;
  switch(fmt) {
    case "0": return Math.round(val);
    case "0.00": return Math.round(val*100)/100;
    case "#,##0": return commaify(String(Math.round(val)));
    case "#,##0.00": return commaify(String(Math.floor(val))) + "." + Math.round((val-Math.floor(val))*100);

The frac helper function is used for fraction formats (defined below).

    case "# ? / ?": ff = frac(val, 10, true); return ff[0] + " " + ff[1] + "/" + ff[2];  
    case "# ?? / ??": ff = frac(val, 100, true); return ff[0] + " " + ff[1] + "/" + ff[2];  
    default: 
  }
  throw new Error("unsupported format |" + fmt + "|");
};

Evaluating Format Strings

function eval_fmt(fmt, v, opts) {
  var out = [], o = "", i = 0, c = "", lst='t', q = {}, dt;
  fixopts(opts = (opts || {}));
  var hr='H';
  /* Tokenize */
  while(i < fmt.length) {
    switch((c = fmt[i])) {

Text between double-quotes are treated literally, and individual characters are literal if they are preceded by a slash:

      case '"': /* Literal text */
        for(o="";fmt[++i] !== '"';) o += fmt[(fmt[i] === '\\' ? ++i : i)];
        out.push({t:'t', v:o}); break;
      case '\\': out.push({t:'t', v:fmt[++i]}); ++i; break;

The '@' symbol refers to the original text. The ECMA spec is not complete, but Excel does not allow for '@' and non-literal text to appear in the same format. It seems as if they only support one mode. (clearly this is a TODO for excel mode but I'm not convinced that's the right approach)

      case '@': /* Text Placeholder */
        out.push({t:'T', v:v}); ++i; break;

The date codes m,d,y,h,s are standard. There are some special formats like e (era year) that have different behaviors in Japanese/Chinese locales.

      /* Dates */
      case 'm': case 'd': case 'y': case 'h': case 's': case 'e':
        if(!dt) dt = parse_date_code(v, opts);
        o = fmt[i]; while(fmt[++i] === c) o+=c;

For the special case of s.00, the suffix should be swallowed with the s:

        if(c === 's' && fmt[i] === '.' && fmt[i+1] === '0') { o+='.'; while(fmt[++i] === '0') o+= '0'; }

Only the forward corrections are made here. The reverse corrections are made later:

        if(c === 'm' && lst.toLowerCase() === 'h') c = 'M'; /* m = minute */
        if(c === 'h') c = hr;
        q={t:c, v:o}; out.push(q); lst = c; break;

The (poorly documented) rule regarding A/P and AM/PM is that if they show up in the format then all instances of h are considered 12-hour and not 24-hour format (even in cases like hh AM/PM hh hh hh).

However, the undocumented H and HH do appear to reset the AM/PM indicator. It is not implemented at the moment because I am not 100% sure of the rules with the HH/hh jazz. TODO: investigate this further.

      case 'A':
        if(!dt) dt = parse_date_code(v, opts);
        q={t:c,v:"A"};
        if(fmt.substr(i, 3) === "A/P") {q.v = dt.H >= 12 ? "P" : "A"; q.t = 'T'; hr='h';i+=3;}
        else if(fmt.substr(i,5) === "AM/PM") { q.v = dt.H >= 12 ? "PM" : "AM"; q.t = 'T'; i+=5; hr='h'; }
        else q.t = "t";
        out.push(q); lst = c; break;

Conditional and color blocks should be handled at one point (TODO). For now, only the absolute time [h] is captured (using the pseudo-type Z):

      case '[': /* TODO: Fix this -- ignore all conditionals and formatting */
        o = c;
        while(fmt[i++] !== ']') o += fmt[i];
        if(o == "[h]") out.push({t:'Z', v:o}); 
        break;

Number blocks (following the general pattern [0#?][0#?.,E+-%]*) are grouped together:

      /* Numbers */
      case '0': case '#':
        var nn = ""; while("0#?.,E+-%".indexOf(c=fmt[i++]) > -1) nn += c;
        out.push({t:'n', v:nn}); break;

The fraction question mark characters present their own challenges. For example, the number 123.456 under format |??| / |???| |???| foo is |15432| / |125| | | foo:

      case '?':
        o = fmt[i]; while(fmt[++i] === c) o+=c;
        q={t:c, v:o}; out.push(q); lst = c; break;

      default:
        if("$-+/():!^&'~{}<>= ".indexOf(c) === -1)
          throw 'unrecognized character ' + fmt[i] + ' in ' + fmt;
        out.push({t:'t', v:c}); ++i; break;
    }
  }

  /* walk backwards */
  for(i=out.length-1, lst='t'; i >= 0; --i) {
    switch(out[i].t) {
      case 'h': case 'H': out[i].t = hr; lst='h'; break;
      case 'd': case 'y': case 's': case 'M': case 'e': lst=out[i].t; break;
      case 'm': if(lst === 's') out[i].t = 'M'; break;
    }
  }

  /* replace fields */
  for(i=0; i < out.length; ++i) {
    switch(out[i].t) {
      case 't': case 'T': break;
      case 'd': case 'm': case 'y': case 'h': case 'H': case 'M': case 's': case 'A': case 'e': case 'Z': 
        out[i].v = write_date(out[i].t, out[i].v, dt);
        out[i].t = 't'; break;
      case 'n':
        var jj = i+1;
        while(out[jj] && (out[jj].t == '?' || out[jj].t == 't' && out[jj].v == '/')) {
          out[i].v += ' ' + out[jj].v; delete out[jj]; ++jj
        }
        out[i].v = write_num(out[i].t, out[i].v, v);
        out[i].t = 't'; 
        i = jj; break;
      default: throw "unrecognized type " + out[i].t;
    }
  }

  return out.map(function(x){return x.v;}).join("");
}
SSF._eval = eval_fmt;

There is some overloading of the m character. According to the spec:

If "m" or "mm" code is used immediately after the "h" or "hh" code (for hours) or immediately before the "ss" code (for seconds), the application shall display minutes instead of the month.

var write_date = function(type, fmt, val) {
  switch(type) {
    case 'y': switch(fmt) { /* year */
      case 'y': case 'yy': return pad(val.y % 100,2);
      default: return val.y;
    } break;
    case 'm': switch(fmt) { /* month */
      case 'm': return val.m;
      case 'mm': return pad(val.m,2);
      case 'mmm': return months[val.m-1][1];
      case 'mmmm': return months[val.m-1][2];
      case 'mmmmm': return months[val.m-1][0];
      default: throw 'bad month format: ' + fmt;
    } break;
    case 'd': switch(fmt) { /* day */
      case 'd': return val.d;
      case 'dd': return pad(val.d,2);
      case 'ddd': return days[val.q][0];
      case 'dddd': return days[val.q][1];
      default: throw 'bad day format: ' + fmt;
    } break;
    case 'h': switch(fmt) { /* 12-hour */
      case 'h': return 1+(val.H+11)%12;
      case 'hh': return pad(1+(val.H+11)%12, 2);
      default: throw 'bad hour format: ' + fmt;
    } break;
    case 'H': switch(fmt) { /* 24-hour */
      case 'h': return val.H;
      case 'hh': return pad(val.H, 2);
      default: throw 'bad hour format: ' + fmt;
    } break;
    case 'M': switch(fmt) { /* minutes */
      case 'm': return val.M;
      case 'mm': return pad(val.M, 2);
      default: throw 'bad minute format: ' + fmt;
    } break;
    case 's': switch(fmt) { /* seconds */
      case 's': return val.S;
      case 'ss': return pad(val.S, 2);
      case 'ss.0': console.log(val);
      default: throw 'bad second format: ' + fmt;
    } break;

The Z type refers to absolute time measures:

    case 'Z': switch(fmt) {
      case '[h]': return val.D*24+val.H;
      default: throw 'bad abstime format: ' + fmt;
    } break;

The e format behavior in excel diverges from the spec. It claims that ee should be a two-digit year, but ee in excel is actually the four-digit year:

    /* TODO: handle the ECMA spec format ee -> yy */
    case 'e': { return val.y; } break;
    case 'A': return (val.h>=12 ? 'P' : 'A') + fmt.substr(1);
    default: throw 'bad format type ' + type + ' in ' + fmt;
  }
};

function choose_fmt(fmt, v) {
  if(typeof fmt === "string") fmt = split_fmt(fmt);
  if(typeof v !== "number") return fmt[3];
  return v > 0 ? fmt[0] : v < 0 ? fmt[1] : fmt[2];
}

var format = function format(fmt,v,o) {
  fixopts(o = (o||{}));
  if(fmt === 0) return general_fmt(v, o);
  if(typeof fmt === 'number') fmt = table_fmt[fmt];
  var f = choose_fmt(fmt, v, o);
  return eval_fmt(f, v, o);
};

SSF._choose = choose_fmt;
SSF._table = table_fmt;
SSF.load = function(fmt, idx) { table_fmt[idx] = fmt; };
SSF.format = format;

Fraction Library

The implementation is from our frac library:

var frac = function(x, D, mixed) {
    var n1 = Math.floor(x), d1 = 1;
    var n2 = n1+1, d2 = 1;
    if(x !== n1) while(d1 <= D && d2 <= D) {
        var m = (n1 + n2) / (d1 + d2);
        if(x === m) {
            if(d1 + d2 <= D) d1+=d2, n1+=n2, d2=D+1;
            else if(d1 > d2) d2=D+1;
            else d1=D+1;
            break;
        }
        else if(x < m) n2 = n1+n2, d2 = d1+d2;
        else n1 = n1+n2, d1 = d1+d2;
    }
    if(d1 > D) d1 = d2, n1 = n2;
    if(!mixed) return [0, n1, d1];
    var q = Math.floor(n1/d1);
    return [q, n1 - q*d1, d1];
};

JS Boilerplate

/* ssf.js (C) 2013 SheetJS -- http://sheetjs.com */
var SSF;
(function(SSF){
String.prototype.reverse=function(){return this.split("").reverse().join("");};
var _strrev = function(x) { return String(x).reverse(); };
function fill(c,l) { return new Array(l+1).join(c); }
function pad(v,d){var t=String(v);return t.length>=d?t:(fill(0,d-t.length)+t);}

})(typeof exports !== 'undefined' ? exports : SSF);

})(SSF);

.vocrc and post-commands

#!/bin/bash
npm install
cat tmp/{00_header,opts,consts,frac,general,date,number,main,zz_footer_n}.js > ssf_node.js
cat tmp/{00_header,opts,consts,frac,general,date,number,main,zz_footer}.js > ssf.js

{
  "post": "bash tmp/post.sh"
}

.gitignore
tmp/
node_modules/
.vocrc

.PHONY: test ssf
ssf: ssf.md
        voc ssf.md

test:
        npm test

{
  "name": "ssf",
  "version": "0.2.2",
  "author": "SheetJS",
  "description": "pure-JS library to format data using ECMA-376 spreadsheet Format Codes",
  "keywords": [ "format", "sprintf", "spreadsheet" ],
  "main": "ssf_node.js",
  "dependencies": {
    "voc":"",
    "colors":""
  },
  "devDependencies": {
    "mocha":""
  },
  "repository": { "type":"git", "url":"git://github.com/SheetJS/ssf.git" },
  "scripts": {
    "test": "mocha -R spec"
  },
  "bugs": { "url": "https://github.com/SheetJS/ssf/issues" },
  "license": "Apache-2.0",
  "engines": { "node": ">=0.8" }
}

Test Driver

Travis CI is used for node testing:

language: node_js
node_js:
  - "0.10"
  - "0.8"
before_install:
  - "npm install -g mocha"

The mocha test driver tests the implied formats:

/* vim: set ts=2: */
var SSF = require('../');
var fs = require('fs'), assert = require('assert');
var data = JSON.parse(fs.readFileSync('./test/implied.json','utf8'));
var skip = [47, 48];
describe('implied formats', function() {
  data.forEach(function(d) {
    it(d[1]+" for "+d[0], skip.indexOf(d[1]) > -1 ? null : function(){
      assert.equal(SSF.format(d[1], d[0], {}), d[2]);
    });
  });
});

The old test driver was manual:

var SSF = require('../ssf_node');
var x = 'd\\-mmm\\-yy\\ yyyy\\ dd\\ \\;\\ yy\\ mm\\ dd';
var y = 'd\\-mmm\\-yy\\ yyyy\\ dd\\ ;\\ yy\\ mm\\ dd';
var z = 'd\\ dd\\ ddd\\ dddd\\ m\\ mm\\ mmm\\ mmmm\\ mmmmm\\ yy\\ yyyy';
console.error(SSF.parse_date_code(65.9));
console.error(SSF.format(x, 65.9));
console.error(SSF.format(y, 65.9));
console.error()
console.error(SSF.format(z, 55.9));
console.error(SSF.format(z, 55.9, {mode:"excel"}));
console.error(SSF.format(z, 55.9));
console.error()
console.error(SSF.format(z, 65.9));
console.error(SSF.format(z, 65.9, {mode:"excel"}));
console.error(SSF.format(z, 65.9));
console.error()
console.error(SSF.format(19, 65.9));
console.error(SSF.format(20, 65.9));

LICENSE

Copyright 2013   SheetJS

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.