@formatjs/ecma402-abstract/NumberFormat/ComputeExponentForMagnitude.js

A collection of implementation for ECMAScript abstract operations

import "../types/number.js";
import { invariant } from "../utils.js";
import { getPowerOf10 } from "./decimal-cache.js";
/**
* The abstract operation ComputeExponentForMagnitude computes an exponent by which to scale a
* number of the given magnitude (power of ten of the most significant digit) according to the
* locale and the desired notation (scientific, engineering, or compact).
*/
export function ComputeExponentForMagnitude(internalSlots, magnitude) {
	const { notation, dataLocaleData, numberingSystem } = internalSlots;
	switch (notation) {
		case "standard": return 0;
		case "scientific": return magnitude.toNumber();
		case "engineering":
			const thousands = magnitude.div(3).floor();
			return thousands.times(3).toNumber();
		default: {
			invariant(notation === "compact", "Invalid notation");
			// Let exponent be an implementation- and locale-dependent (ILD) integer by which to scale a
			// number of the given magnitude in compact notation for the current locale.
			const { compactDisplay, style, currencyDisplay } = internalSlots;
			let thresholdMap;
			if (style === "currency" && currencyDisplay !== "name") {
				const currency = dataLocaleData.numbers.currency[numberingSystem] || dataLocaleData.numbers.currency[dataLocaleData.numbers.nu[0]];
				thresholdMap = currency.short;
			} else {
				const decimal = dataLocaleData.numbers.decimal[numberingSystem] || dataLocaleData.numbers.decimal[dataLocaleData.numbers.nu[0]];
				thresholdMap = compactDisplay === "long" ? decimal.long : decimal.short;
			}
			if (!thresholdMap) {
				return 0;
			}
			const num = getPowerOf10(magnitude).toString();
			const thresholds = Object.keys(thresholdMap);
			if (num < thresholds[0]) {
				return 0;
			}
			if (num > thresholds[thresholds.length - 1]) {
				// GH #4236: When number exceeds max threshold, use the exponent
				// corresponding to the largest available threshold in locale data.
				// Calculate exponent the same way as for normal thresholds (lines 70-73).
				const magnitudeKey = thresholds[thresholds.length - 1];
				const compactPattern = thresholdMap[magnitudeKey].other;
				if (compactPattern === "0") {
					return 0;
				}
				return magnitudeKey.length - thresholdMap[magnitudeKey].other.match(/0+/)[0].length;
			}
			const i = thresholds.indexOf(num);
			if (i === -1) {
				return 0;
			}
			// See https://unicode.org/reports/tr35/tr35-numbers.html#Compact_Number_Formats
			// Special handling if the pattern is precisely `0`.
			const magnitudeKey = thresholds[i];
			// TODO: do we need to handle plural here?
			const compactPattern = thresholdMap[magnitudeKey].other;
			if (compactPattern === "0") {
				return 0;
			}
			// Example: in zh-TW, `10000000` maps to `0000萬`. So we need to return 8 - 4 = 4 here.
			return magnitudeKey.length - thresholdMap[magnitudeKey].other.match(/0+/)[0].length;
		}
	}
}