woocommerce-paypal-payments/modules/ppcp-settings/resources/js/utils/Helper/FormHelper.js

/**
 * Common Form utility methods
 */
export default class FormHelper {
	static getPrefixedFields( formElement, prefix ) {
		const formData = new FormData( formElement );
		const fields = {};

		for ( const [ name, value ] of formData.entries() ) {
			if ( ! prefix || name.startsWith( prefix ) ) {
				fields[ name ] = value;
			}
		}

		return fields;
	}

	static getFilteredFields( formElement, exactFilters, prefixFilters ) {
		const formData = new FormData( formElement );
		const fields = {};
		const counters = {};

		for ( let [ name, value ] of formData.entries() ) {
			// Handle array format
			if ( name.indexOf( '[]' ) !== -1 ) {
				const k = name;
				counters[ k ] = counters[ k ] || 0;
				name = name.replace( '[]', `[${ counters[ k ] }]` );
				counters[ k ]++;
			}

			if ( ! name ) {
				continue;
			}
			if ( exactFilters && exactFilters.indexOf( name ) !== -1 ) {
				continue;
			}
			if (
				prefixFilters &&
				prefixFilters.some( ( prefixFilter ) =>
					name.startsWith( prefixFilter )
				)
			) {
				continue;
			}

			fields[ name ] = value;
		}

		return fields;
	}
}