echarts tooltip 文字过长 ，折行显示

            tooltip: {
                trigger: 'item',
                position: 'top',
                confine:true ,
                formatter: "{a} <br/> "+ "<div style='display:block;word-break: break-all;word-wrap: break-word;white-space:pre-wrap'>" + "{b} " + "</div>" + " <br/>{c}" ,
            },