messageformat-number-skeleton/lib/numberformat/modifier.js

A parser & formatter for ICU NumberFormat skeleton strings & patterns

// from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/round
function round(x, precision) {
    const y = +x + precision / 2;
    return y - (y % +precision);
}
function getNumberFormatMultiplier({ scale, unit }) {
    let mult = typeof scale === 'number' && scale >= 0 ? scale : 1;
    if (unit && unit.style === 'percent')
        mult *= 0.01;
    return mult;
}
/**
 * Determine a modifier for the input value to account for any `scale`,
 * `percent`, and `precision-increment` tokens in the skeleton.
 *
 * @internal
 * @remarks
 * With ICU NumberFormatter, the `percent` skeleton would style `25` as "25%".
 * To achieve the same with `Intl.NumberFormat`, the input value must be `0.25`.
 */
export function getNumberFormatModifier(skeleton) {
    const mult = getNumberFormatMultiplier(skeleton);
    const { precision } = skeleton;
    if (precision && precision.style === 'precision-increment') {
        return (n) => round(n, precision.increment) * mult;
    }
    else {
        return (n) => n * mult;
    }
}
/**
 * Returns a string of JavaScript source that evaluates to a modifier for the
 * input value to account for any `scale`, `percent`, and `precision-increment`
 * tokens in the skeleton.
 *
 * @internal
 * @remarks
 * With ICU NumberFormatter, the `percent` skeleton would style `25` as "25%".
 * To achieve the same with `Intl.NumberFormat`, the input value must be `0.25`.
 */
export function getNumberFormatModifierSource(skeleton) {
    const mult = getNumberFormatMultiplier(skeleton);
    const { precision } = skeleton;
    if (precision && precision.style === 'precision-increment') {
        // see round() above for source
        const setX = `+n + ${precision.increment / 2}`;
        let res = `x - (x % +${precision.increment})`;
        if (mult !== 1)
            res = `(${res}) * ${mult}`;
        return `function(n) { var x = ${setX}; return ${res}; }`;
    }
    return mult !== 1 ? `function(n) { return n * ${mult}; }` : null;
}