jquery-js 集合(数组)去重，交集，并集，差集

1. js 实现数组的集合运算

  // 去重
  function array_remove_repeat(a) { 
    var r = [];
    for(var i = 0; i < a.length; i ++) {
        var flag = true;
        var temp = a[i];
        for(var j = 0; j < r.length; j ++) {
            if(temp === r[j]) {
                flag = false; break;
            }
        }
    if(flag) {
        r.push(temp); }
    }
    return r;
  }

  // 交集 
  function array_intersection(a, b) { 
      var result = []; 
      for(var i = 0; i < b.length; i ++) { 
           var temp = b[i]; 
           for(var j = 0; j < a.length; j ++) { 
                 if(temp === a[j]) {  
                        result.push(temp);
                        break; 
                  } 
            } 
        } 
        return array_remove_repeat(result); 
   } 
   
   // 并集 
   function array_union(a, b) { 
      return array_remove_repeat(a.concat(b)); 
   } 
   
   // 差集 a - b 
   function array_difference(a, b) { 
      //clone = a 
      var clone = a.slice(0); 
      for(var i = 0; i < b.length; i ++) { 
           var temp = b[i]; 
           for(var j = 0; j < clone.length; j ++) { 
                if(temp === clone[j]) { 
                    //remove clone[j] 
                   clone.splice(j,1);
                 } 
            } 
        } 
        return array_remove_repeat(clone); 
    } 

//测试
a = [1,2,3,4,5]; 
b = [3,4,5,6,7]; 
c = array_intersection(a, b);
d = array_union(a, b); 
e = array_difference(a, b); 
f = array_difference(b, a); 
console.log("test array a:", a, "  b:", b); 
console.log("a & b :", c); 
console.log("a + b :", d); 
console.log("a - b:", e); 
console.log("b - a:", f);

测试结果：

stephen@stephen:~/openstack/demo/nodejs$ node set_operation.js

test array a: [ 1, 2, 3, 4, 5 ]   b: [ 3, 4, 5, 6, 7 ]

a & b : [ 3, 4, 5 ]

a + b : [ 1, 2, 3, 4, 5, 6, 7 ]

a - b: [ 1, 2 ]

b - a: [ 6, 7 ]

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