不重复的随机数简单示例

<script>
    var arr=[];
    function random(){
        var num=Math.floor(Math.random()*30);
        if(arr.indexOf(num)==-1){
            console.log(num+1)
            arr.push(num)
            return num;
        }else{
            if(arr.length<30){
                random()
            }else{
                console.log("renshu",arr.length,arr)
            }
        }
    }
</script>
<button onclick="random()">点击</button>