js 判断数组是否有重复元素的几种方式

// 方法一，正则判断 var ary = new Array("111","222","33","112","222"); alert(mm(ary)) // 验证重复元素，有重复返回true；否则返回false function mm(a) { return /(\x0f[^\x0f]+)\x0f[\s\S]*\1/.test("\x0f"+ a.join("\x0f\x0f") +"\x0f"); } // 方法二，通过数组排序，比较临近元素，可指出重复的元素 var ary = new Array("111","22","33","111","22"); var nary = ary.sort(); for(var i = 0; i < nary.length - 1; i++) { if (nary[i] == nary[i+1]) { alert("重复内容：" + nary[i]); } } // 方法三，通过字符串查找 var ary = new Array("111","22","33","111","22"); var s = ary.join(",") + ","; for(var i = 0; i < ary.length; i++) { if(s.replace(ary[i] + ",", "").indexOf(ary[i] + ",") > -1) { alert("重复内容：" + ary[i]); } } // 方法四，通过哈希 var ary = new Array("111","22","33","111","22"); alert(isRepeat(ary)); // 验证重复元素，有重复返回true；否则返回false function isRepeat(arr) { var hash = {}; for(var i in arr) { if(hash[arr[i]]) { return true; } // 不存在该元素，则赋值为true，可以赋任意值，相应的修改if判断条件即可 hash[arr[i]] = true; } return false; }