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77 lines
3.0 KiB
77 lines
3.0 KiB
/**
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* Here are the most relevant formats we want to support.
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* -1234.56 Plain
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* -1,234.56 Number (with separators)
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* 12.34% Percent
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* 1.23E3 Scientific
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* $(1,234.56) Accounting
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* (1,234.56) Financial
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* -$1,234.56 Currency
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*
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* We implement a button-based UI, using one selector button to choose mode:
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* none = NumMode undefined (plain number, no thousand separators)
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* `$` = NumMode 'currency'
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* `,` = NumMode 'decimal' (plain number, with thousand separators)
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* `%` = NumMode 'percent'
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* `Exp` = NumMode 'scientific'
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* A second toggle button is `(-)` for Sign, to use parentheses rather than "-" for negative
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* numbers. It is Ignored and disabled when mode is 'scientific'.
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*/
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import {clamp} from 'app/common/gutil';
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// Options for number formatting.
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export type NumMode = 'currency' | 'decimal' | 'percent' | 'scientific';
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export type NumSign = 'parens';
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// TODO: In the future, locale should be a value associated with the document or the user.
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const defaultLocale = 'en-US';
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// TODO: The currency to use for currency formatting could be made configurable.
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const defaultCurrency = 'USD';
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export interface NumberFormatOptions {
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numMode?: NumMode;
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numSign?: NumSign;
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decimals?: number; // aka minimum fraction digits
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maxDecimals?: number;
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}
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export function buildNumberFormat(options: NumberFormatOptions): Intl.NumberFormat {
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const nfOptions: Intl.NumberFormatOptions = parseNumMode(options.numMode);
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// numSign is implemented outside of Intl.NumberFormat since the latter's similar 'currencySign'
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// option is not well-supported, and doesn't apply to non-currency formats.
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if (options.decimals !== undefined) {
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// Should be at least 0
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nfOptions.minimumFractionDigits = clamp(Number(options.decimals), 0, 20);
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}
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// maximumFractionDigits must not be less than the minimum, so we need to know the minimum
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// implied by numMode.
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const tmp = new Intl.NumberFormat(defaultLocale, nfOptions).resolvedOptions();
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if (options.maxDecimals !== undefined) {
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// Should be at least 0 and at least minimumFractionDigits.
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nfOptions.maximumFractionDigits = clamp(Number(options.maxDecimals), tmp.minimumFractionDigits || 0, 20);
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} else if (!options.numMode) {
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// For the default format, keep max digits at 10 as we had before.
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nfOptions.maximumFractionDigits = clamp(10, tmp.minimumFractionDigits || 0, 20);
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}
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return new Intl.NumberFormat(defaultLocale, nfOptions);
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}
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function parseNumMode(numMode?: NumMode): Intl.NumberFormatOptions {
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switch (numMode) {
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case 'currency': return {style: 'currency', currency: defaultCurrency};
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case 'decimal': return {useGrouping: true};
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case 'percent': return {style: 'percent'};
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// TODO 'notation' option (and therefore numMode 'scientific') works on recent Firefox and
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// Chrome, not on Safari or Node 10.
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case 'scientific': return {notation: 'scientific'} as Intl.NumberFormatOptions;
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default: return {useGrouping: false};
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}
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}
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