JSON中指定值的最大值与最小值
let max = Math.max.apply( Math,this.stuRadarChartList.map(function (o) { return o.num }) )
let min = Math.min.apply(Math,this.stuRadarChartList.map(function(o) { return o.num; }))
let max = Math.max.apply( Math,this.stuRadarChartList.map(function (o) { return o.num }) )
let min = Math.min.apply(Math,this.stuRadarChartList.map(function(o) { return o.num; }))