for循环indexof() var a=[1, 2, 2, 3, 4, 2, 2,5,36,4,78,3,3,3,3]; var b=[]; for (var i =0; i <a.length; i++) { if(b.indexOf(a[i])==-1 && a.indexOf(a[i])!==a.lastIndexOf(a[i])){ b.push(a[i]); } } console.log(b);