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我受够了有限的 javascript Array 函数，想编写一些我自己方便的原型函数来执行 Set Theory 函数。

下面是我到目前为止的代码 

<script type="text/javascript">

Array.prototype.contains = function(obj) {
    var i = this.length;
    while (i--) {
        if (this[i] === obj) {
            return true;
        }
    }
    return false;
}

Array.prototype.getIndices = function(obj){
    var indices = new Array();
    var i = this.length;
    while (i--) {
        if(this[i] === obj){
            indices.push(i);
        }
    }
    return indices;
}

Array.prototype.Union = function(arr){
    //combines two arrays together to return a single array containing all elements (once)
    //{1,2,3,4,5}.Union({3,4,5,6,7})
    //returns: {1,2,3,4,5,6,7}
        var primArray = this;
        var secondArray = arr;
    var i = primArray.length;
    while(i--){
        if(secondArray.contains(primArray[i])){
            primArray.splice(i, 1);
        }
    }
    var returnArr = primArray.concat(secondArray);
    return returnArr;
}

Array.prototype.Intersection = function(arr){
    //Returns an array of elements that are present in both sets
    //{1,2,3,4,5}.Intersection({3,4,5,6,7})
    //returns: {3,4,5}
        var primArray = this;
        var secondArray = arr;
    var returnArr = new Array;
    var i = 0;
    while(i++<primArray.length){
        if(secondArray.contains(primArray[i])){
            returnArr.push(primArray[i]);
        }
    }
    return returnArr;
}

Array.prototype.Complement = function(arr){
    //Returns an array of elements that are only in the primary (calling) element
    //{1,2,3,4,5}.Complement({3,4,5,6,7})
    //return: {1,2}
        var primArray = this;
        var secondArray = arr;
    var i = primArray.length;
    while(i--){
        if(secondArray.contains(primArray[i])){
            primArray.splice(i, 1);
        }
    }
    return primArray;
}

Array.prototype.SymmetricDifference = function(arr){
    //Returns elements that are exclusive to each set
    //{1,2,3,4,5}.SymmetricDifference({3,4,5,6,7})
    //return: {1,2,6,7}
        var primArray = this;
        var secondArray = arr;
    var i = primArray.length;
    while(i--){
        if(secondArray.contains(primArray[i])){
            var indices = secondArray.getIndices(primArray[i]);
            primArray.splice(i, 1);
            var j=indices.length;
            while(j--){
                secondArray.splice(indices[j], 1);
            }
        }
    }
    var returnArr = primArray.concat(arr);
    return returnArr;
}

function run(){
     var Q = "A";
     var D = [1,2,3,4,5,6,7,8,9,10];
     var sets = {
          "A":[1,2,3],
          "B":[3,4,5],
          "C":[5,6,7]
     }
     var R = D;
     for(var el in sets){
          R = R.Complement(sets[el]);
     }
//if I alert D at this point I get 8,9,10 instead of 1,2,3,4,5,6,7,8,9,10 as I would expect? What am I missing here... It causes a problem when I perform D.Complement(R) later on
     document.write(R + "<br/>");
     R = R.Union(sets[Q]);
     document.write(R + "<br/>");
  //Here!  
     R = D.Complement(R);
     document.write(R);
}

</script>

</head>

<body onload="run()">

</body>
</html>

当我尝试获得域的补集和我新构建的集合时，一切都在工作到最后一点。我预计将得到 [1,2,3,4,5,6,7,8,9,10] 和 [8,9,10,1,2,3] 的补码，这将产生 [4, 5,6,7] 但是当我执行 D.Complement(R) 时，我的 D 变量似乎变成了 [1,2,3]。这似乎发生在我执行的枚举之后。

我认为这可能是因为我在函数中使用了 this.splice 和 arr.splice，当我将变量传递给函数时，它们作为指针传递，这意味着我实际上是在处理实际的内存位置。所以我然后使用 primArray 和 secondArray 创建一个副本来处理......但问题仍然存在

非常感谢

4

1 回答 1

1

所以我然后使用 primArray 和 secondArray 创建一个副本来处理......但问题仍然存在

只是将它分配给一个变量并不会使它成为一个新数组，您仍在处理传入的数组。您必须通过循环并复制每个索引或加入并手动制作数组的新副本分裂。

于 2010-12-13T15:59:56.620 回答