node_modules/tui-dom/src/js/domevent.js
/**
 * Normalize return value of mouseEvent.button
 * Make same to standard MouseEvent's button value
 * @param {DispCEventObj} mouseEvent - mouse event object
 * @returns {number|null} - id indicating which mouse button is clicked
 * @private
 */
Normalize return value of mouseEvent.button
Make same to standard MouseEvent's button value
@param {DispCEventObj} mouseEvent - mouse event object
@returns {number|null} - id indicating which mouse button is clicked
@private
Normalize return value of mouseEvent . button Make same to standard MouseEvent ' s button value @param { DispCEventObj } mouseEvent - mouse event object @returns { number|null } - id indicating which mouse button is clicked @private
function _getMouseButtonIE8AndEarlier(mouseEvent) {
    const button = String(mouseEvent.button);
    if (util.inArray(button, primaryButton) > -1) {
        return 0;
    } else if (util.inArray(button, secondaryButton) > -1) {
        return 2;
    } else if (util.inArray(button, wheelButton) > -1) {
        return 1;
    }
    return null;
}
function _getMouseButtonIE8AndEarlier ( mouseEvent ) { const button = String ( mouseEvent . button ) ; if ( util . inArray ( button , primaryButton ) > - 1 ) { return 0 ; } else if ( util . inArray ( button , secondaryButton ) > - 1 ) { return 2 ; } else if ( util . inArray ( button , wheelButton ) > - 1 ) { return 1 ; } return null ; }
Normalize return value of mouseEvent.button
 Make same to standard MouseEvent's button value
 @param {DispCEventObj} mouseEvent - mouse event object
 @returns {number|null} - id indicating which mouse button is clicked
 @private
Normalize return value of mouseEvent . button Make same to standard MouseEvent ' s button value @param { DispCEventObj } mouseEvent - mouse event object @returns { number|null } - id indicating which mouse button is clicked @private