aureooms/es-parse

/**
 * Converts as many tokens as possible into an integer.
 * @param {Stream} stream - The stream to read from.
 */
export default function integer ( stream ) {

    let i = 0 ;
    let s = 1 ;

    const token = stream.read( ) ;

    if ( token === stream.eof ) return stream.eof ;

    if ( token === '-' ) s = -1 ;
    else if ( token !== '+' ) stream.unread( token ) ;

    while ( true ) {

        const token = stream.read( ) ;

        if ( token === stream.eof ) return s * i ;

        if ( token < '0' || token > '9' ) {
            stream.unread( token ) ;
            return s * i ;
        }

        i *= 10 ;
        i += +token ;

    }

}