js-d3-zoom怎么区分平移和缩放

var velocity = 1 / 5;

var scale = Math.pow(d3.event.transform.k, velocity);

var translateY = d3.event.transform.y * velocity;

var translateX = d3.event.transform.x * velocity;



_this.svg.d3.selectAll('rect,path,g,text').attr('transform',

        'translate(' + translateX + ',' + translateY + ') scale(' + scale + ')'

)