var id=null;var random= Math.random();if(random< 0.1) id= 0;else if(random< 0.3)    id= 1;else if(random< 0.35)    id= 2;else if(random< 0.65)    id = 3else if(random< 0.7)    id = 4;else if(random< 0.75) id= 5;else if(random< 0.8)  id= 6;else if(random< 0.9)id= 7;else if(random< 0.95)id= 8;else if(random< 1) id= 9;alert(id)

当0<=random<0.1(区间跨度0.1)             id = 0;当0.1<=random<0.3(区间跨度0.2)            id = 1;当0.3<=random<0.35(区间跨度0.05)      id = 2;当0.35<=random<0.65(区间跨度0.3)        id = 3;当0.65<=random<0.7(区间跨度0.05)       id = 4;当0.7<=random<0.75(区间跨度0.05)       id = 5;当0.75<=random<0.8(区间跨度0.05)       id = 6当0.8<=random<0.9(区间跨度0.1)           id = 7当0.9<=random<0.95(区间跨度0.05)     id = 8当0.95<=random<1(区间跨度0.05)         id =9