JS：重量单位换算

//单位换算：数量，原单位，目标单位
var GetNumByUnit = function (num, unitname,outunitname) {
var fRate = {//换算率
ng: { μg: 0.001, mg: 0.001 * 0.001, g: 0.001 * 0.001 * 0.001, kg: 0.001 * 0.001 * 0.001 * 0.001, t: 0.001 * 0.001 * 0.001 * 0.001 * 0.001, ul: 0.001 * 0.001, ml: 0.001 * 0.001 * 0.001, L: 0.001 * 0.001 * 0.001 * 0.001 },
μg: { ng: 1000, mg: 0.001, g: 0.001 * 0.001, kg: 0.001 * 0.001 * 0.001, t: 0.001 * 0.001 * 0.001 * 0.001, ul:0.001, ml:0.001 * 0.001, L:0.001 * 0.001 * 0.001 },
mg: { ng: 1000 * 1000, μg: 1000, g: 0.001, kg: 0.001 * 0.001, t:0.001 * 0.001 * 0.001, ul:1, ml: 0.001, L: 0.001 * 0.001 },
g: { ng: 1000 * 1000*1000, μg: 1000*1000, mg:1000, kg: 0.001, t: 0.001 * 0.001, ul: 1000 , ml: 1, L: 0.001 },
kg: { ng: 1000 * 1000 * 1000 * 1000, μg: 1000 * 1000, mg: 1000, g: 1000, t: 0.001 , ul: 1000 * 1000 , ml: 1000, L: 1 },
t: { ng: 1000 * 1000 * 1000 * 1000 * 1000, μg: 1000 * 1000 * 1000, mg: 1000 * 1000, g: 1000 * 1000, kg: 1000, ul: 1000 * 1000 * 1000, ml: 1000 * 1000, L: 1000 },
ml: { ng: 1000 * 1000 * 1000, μg: 1000 * 1000, mg: 1000, g: 1, kg: 0.001, t: 0.001 * 0.001, ul: 1000 , L: 0.001 },
ul: { ng: 1000 * 1000, μg: 1000, ml: 1, g: 0.001, kg: 0.001 * 0.001, t: 0.001 * 0.001 * 0.001, ml: 0.001, L: 0.001 * 0.001 },
L: { ng: 1000 * 1000 * 1000 * 1000, μg: 1000 * 1000, mg: 1000, g: 1000,kg:1, t: 0.001, ul: 1000 * 1000, ml: 1000 },
};
var tnum = (num * fRate[unitname][outunitname]).toFixed(4);
return tnum;
};