woocommerce-paypal-payments/modules/ppcp-button/resources/js/modules/Helper/CardFieldsHelper.js

export const cardFieldStyles = (field) => {
    const allowedProperties = [
        'appearance',
        'color',
        'direction',
        'font',
        'font-family',
        'font-size',
        'font-size-adjust',
        'font-stretch',
        'font-style',
        'font-variant',
        'font-variant-alternates',
        'font-variant-caps',
        'font-variant-east-asian',
        'font-variant-ligatures',
        'font-variant-numeric',
        'font-weight',
        'letter-spacing',
        'line-height',
        'opacity',
        'outline',
        'padding',
        'padding-bottom',
        'padding-left',
        'padding-right',
        'padding-top',
        'text-shadow',
        'transition',
        '-moz-appearance',
        '-moz-osx-font-smoothing',
        '-moz-tap-highlight-color',
        '-moz-transition',
        '-webkit-appearance',
        '-webkit-osx-font-smoothing',
        '-webkit-tap-highlight-color',
        '-webkit-transition',
    ];

    const stylesRaw = window.getComputedStyle(field);
    const styles = {};
    Object.values(stylesRaw).forEach((prop) => {
        if (!stylesRaw[prop] || !allowedProperties.includes(prop)) {
            return;
        }
        styles[prop] = '' + stylesRaw[prop];
    });

    return styles;
}