1  'use strict';
 2  
 3  module.exports = function union(init) {
 4    if (!Array.isArray(init)) {
 5      throw new TypeError('arr-union expects the first argument to be an array.');
 6    }
 7  
 8    var len = arguments.length;
 9    var i = 0;
10  
11    while (++i < len) {
12      var arg = arguments[i];
13      if (!arg) continue;
14  
15      if (!Array.isArray(arg)) {
16        arg = [arg];
17      }
18  
19      for (var j = 0; j < arg.length; j++) {
20        var ele = arg[j];
21  
22        if (init.indexOf(ele) >= 0) {
23          continue;
24        }
25        init.push(ele);
26      }
27    }
28    return init;
29  };