<script>
function selectForm(lowerValue,upperValue){
var choices=upperValue-lowerValue+1;
return Math.floor(Math.random()*choices+lowerValue)
}
var colors=["red","green","blue","yellow","black","purple","brown"];
var color=colors[selectForm(0,colors.length-1)];
alert(color);
</script>
PS：如果不懂，可查阅《JS高程》 P136