新解决方案（使用Array.prototype.indexOf和Array.prototype.cocat）：

Array.prototype.uniqueMerge = function( a ) {
    for ( var nonDuplicates = [], i = 0, l = a.length; i<l; ++i ) {
        if ( this.indexOf( a[i] ) === -1 ) {
            nonDuplicates.push( a[i] );
        }
    }
    return this.concat( nonDuplicates )
};

用法：

>>> ['Vijendra', 'Singh'].uniqueMerge(['Singh', 'Shakya'])
["Vijendra", "Singh", "Shakya"]

Array.prototype.indexOf（用于internet explorer）：

Array.prototype.indexOf = Array.prototype.indexOf || function(elt)
  {
    var len = this.length >>> 0;

    var from = Number(arguments[1]) || 0;
    from = (from < 0) ? Math.ceil(from): Math.floor(from); 
    if (from < 0)from += len;

    for (; from < len; from++)
    {
      if (from in this && this[from] === elt)return from;
    }
    return -1;
  };

为什么不使用对象？看起来你在尝试建立一套模型。然而，这并不能维持秩序。

var set1 = {"Vijendra":true, "Singh":true}
var set2 = {"Singh":true,  "Shakya":true}

// Merge second object into first
function merge(set1, set2){
  for (var key in set2){
    if (set2.hasOwnProperty(key))
      set1[key] = set2[key]
  }
  return set1
}

merge(set1, set2)

// Create set from array
function setify(array){
  var result = {}
  for (var item in array){
    if (array.hasOwnProperty(item))
      result[array[item]] = true
  }
  return result
}

最佳解决方案。。。

您可以直接在浏览器控制台中点击。。。

无重复项

a = [1, 2, 3];
b = [3, 2, 1, "prince"];

a.concat(b.filter(function(el) {
    return a.indexOf(el) === -1;
}));

具有重复项

["prince", "asish", 5].concat(["ravi", 4])

如果你想要没有重复，你可以从这里尝试一个更好的解决方案-大喊代码。

[1, 2, 3].concat([3, 2, 1, "prince"].filter(function(el) {
    return [1, 2, 3].indexOf(el) === -1;
}));

在Chrome浏览器控制台上试用

 f12 > console

输出：

["prince", "asish", 5, "ravi", 4]

[1, 2, 3, "prince"]

关心效率，但想在线实现

const s = new Set(array1);
array2.forEach(a => s.add(a));
const merged_array = [...s]; // optional: convert back in array type

新解决方案（使用Array.prototype.indexOf和Array.prototype.cocat）：

Array.prototype.uniqueMerge = function( a ) {
    for ( var nonDuplicates = [], i = 0, l = a.length; i<l; ++i ) {
        if ( this.indexOf( a[i] ) === -1 ) {
            nonDuplicates.push( a[i] );
        }
    }
    return this.concat( nonDuplicates )
};

用法：

>>> ['Vijendra', 'Singh'].uniqueMerge(['Singh', 'Shakya'])
["Vijendra", "Singh", "Shakya"]

Array.prototype.indexOf（用于internet explorer）：

Array.prototype.indexOf = Array.prototype.indexOf || function(elt)
  {
    var len = this.length >>> 0;

    var from = Number(arguments[1]) || 0;
    from = (from < 0) ? Math.ceil(from): Math.floor(from); 
    if (from < 0)from += len;

    for (; from < len; from++)
    {
      if (from in this && this[from] === elt)return from;
    }
    return -1;
  };

对于n个数组，可以这样得到并集。

function union(arrays) {
    return new Set(arrays.flat()).keys();
};