[Proposal] Compact Decimal Format to abbreviate large numbers

[caridy]

CLDR contains the details to abbreviate large numbers, e.g.:

        "decimalFormats-numberSystem-latn": {
          "standard": "#,##0.###",
          "long": {
            "decimalFormat": {
              "1000-count-one": "0 thousand",
              "1000-count-other": "0 thousand",
              "10000-count-one": "00 thousand",
              "10000-count-other": "00 thousand",
              "100000-count-one": "000 thousand",
              "100000-count-other": "000 thousand",
              "1000000-count-one": "0 million",
              "1000000-count-other": "0 million",
              "10000000-count-one": "00 million",
              "10000000-count-other": "00 million",
              "100000000-count-one": "000 million",
              "100000000-count-other": "000 million",
              "1000000000-count-one": "0 billion",
              "1000000000-count-other": "0 billion",
              "10000000000-count-one": "00 billion",
              "10000000000-count-other": "00 billion",
              "100000000000-count-one": "000 billion",
              "100000000000-count-other": "000 billion",
              "1000000000000-count-one": "0 trillion",
              "1000000000000-count-other": "0 trillion",
              "10000000000000-count-one": "00 trillion",
              "10000000000000-count-other": "00 trillion",
              "100000000000000-count-one": "000 trillion",
              "100000000000000-count-other": "000 trillion"
            }
          },
          "short": {
            "decimalFormat": {
              "1000-count-one": "0K",
              "1000-count-other": "0K",
              "10000-count-one": "00K",
              "10000-count-other": "00K",
              "100000-count-one": "000K",
              "100000-count-other": "000K",
              "1000000-count-one": "0M",
              "1000000-count-other": "0M",
              "10000000-count-one": "00M",
              "10000000-count-other": "00M",
              "100000000-count-one": "000M",
              "100000000-count-other": "000M",
              "1000000000-count-one": "0B",
              "1000000000-count-other": "0B",
              "10000000000-count-one": "00B",
              "10000000000-count-other": "00B",
              "100000000000-count-one": "000B",
              "100000000000-count-other": "000B",
              "1000000000000-count-one": "0T",
              "1000000000000-count-other": "0T",
              "10000000000000-count-one": "00T",
              "10000000000000-count-other": "00T",
              "100000000000000-count-one": "000T",
              "100000000000000-count-other": "000T"
            }
          }
        },

@rxaviers proposed this feature a while ago IIRC, but I could find the thread, so I'm posting it here to formalize the proposal.

Proposal

This proposal goes hand-to-hand with the pluralization (#34) since it will have to compute what's the pluralization token to choose the right format (In the CLDR data you will see that for english we have a lot of *-count-one and *-count-other).

The initial proposal could be to add one more configuration to specify either:

a) best-fit for the abbreviation, which means we choose the biggest matching decimal from the segments
b) the decimal reference to force to use a particular formatting option (e.g.: 10000, which could produce 1234K);

new Intl.NumberFormat('en', { compact: 'best-fit' }).format(1234000); // 1.2M
new Intl.NumberFormat('en', { compact: '4-digits' }).format(1234000); // 1234K

Open questions

• how to match this with currency values so we can produce something like $12M.
• the name of the configuration option when creating a new Intl.NumberFormat()
• 1M vs 1.2M
• 1M vs 1 Million (this will probably require another configuration to specify long vs short.
• rounding and custom rounding settings? (related to Proposal for stage 0 rxaviers/ecma402-number-format-round-option#1 (comment))

/cc @jfparadis @zbraniecki

[caridy]

More details about CLDR Compact Decimal Format here: http://www.unicode.org/cldr/charts/27/summary/pl.html#4032

[zbraniecki]

Probably same algorithm will be useful as for issue #32. ("1.2 M" vs. "2.5 KB")

[srl295]

Spec: UTS #35 (HEAD)

[rxaviers]

cc @steveluscher due to its related proposal https://gist.github.com/steveluscher/4b54e08aa1e0536b7cb9

[steveluscher]

Can you link to this rounding discussion in your list of open questions, @caridy?

[caridy]

@steveluscher added.

[charoseth]

Any progress/plan for this proposal?
This is quite useful for some statistical data shown in analysis softwares for localization.