SOURCE

    var arr = new Array(20);
    for (var i = 0; i < arr.length; i++) {
        arr[i] = Math.ceil(Math.random() * 10);
    }
    console.log(arr);
    var a=[]
    for(i of arr){
        if(a.indexOf(i) != -1) continue
        // console.log(a.indexOf(i))
        b = arr.filter((item)=>{
            // console.log(item)
            return i === item
        })
        a.push(i)
        // console.log(b)
        // console.log(b.length)
        len = b.length
        
        if(len <=1 ) continue
        console.log('重复元素：'+i)
        console.log('重复数量：'+len)
        console.log('')
        
    }