Three JS ways to determine whether an array has duplicate values

This article mainly brings you three JS methods to determine whether an array has duplicate values. It is mainly shared with you in the form of code. Students in need can learn from it. I hope it can help everyone.

Method one:

var s = ary.join(",")+",";
for(var i=0;i<ary.length;i++) {
if(s.replace(ary[i]+",","").indexOf(ary[i]+",")>-1) {
alert("数组中有重复元素：" + ary[i]);
break;
}
}

Method two:

var ary = new Array("111","22","33","111");
var nary=ary.sort();
for(var i=0;i<ary.length;i++){
if (nary[i]==nary[i+1]){
alert("数组重复内容："+nary[i]);
}
}

Method 3:

function isRepeat(arr){
var hash = {};
for(var i in arr) {
if(hash[arr[i]])
return true;
hash[arr[i]] = true;
}
return false;
}

Related links:

js determines whether the array has duplicate values

determines whether the array elements are duplicates

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