JavaScript獲取多個數組的交集簡單實例

2019-11-20 21:44:14

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在項目中需要取得多個數組的交集，故本例只是適用于特定場景。比如A數組 var a = {1000,10001,10002,10003}; B數組 var b = {10002, 10003}; C數組var c = {10003}; 需要取得這三個數組的交集數組。
具體思路為：先初始一個最小數組為A數組,元素個數最小的也是數組A的長度.然后再迭代各個數組,取得這幾個數組長度最短的為最小長度,同時得到長度最短數組。然后,迭代最小數組與各個數組,開始比較元素相等,使用計數器來判斷是否該元素在各個數組中都存在即為交集元素.
思路比較簡單,但是可以實現多數組取得交集,代碼如下：

復制代碼代碼如下:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> 
<HTML> 
 <HEAD> 
  <TITLE> New Document </TITLE> 
  <META NAME="Generator" CONTENT="EditPlus"> 
  <META NAME="Author" CONTENT=""> 
  <META NAME="Keywords" CONTENT=""> 
  <META NAME="Description" CONTENT=""> 
  <script> 
        function getValues(obj){     
            var values = ""; 
            var l = obj.options.length; 
            for (var i=0; i<l; i++) { 
                if (i != (l-1)) { 
                    values += obj.options(i).value + "_"; 
                } 
                else { 
                    values += obj.options(i).value; 
                } 
            } 
            return values; 
        } 

        function _test() { 
            var ids = getValues(document.all.aa); 
            var aa = _getIntersection(ids); 
        } 

        function _getIntersection(src) { 
            var tAry = src.split("_"); 
            //最小數組 
            var minAry = null; 
            var min = tAry[0].split(",").length; //初始化第一個為長度最小的數組 
            minAry = tAry[0].split(","); 
            for (var i = 1, len = tAry.length; i<len; i++) { 
                var temp = tAry[i].split(","); 
                if (temp.length < min) { 
                    min = temp.length; 
                    minAry = temp; 
                }  
            } 
            alert("最小數組："+minAry); 

            var ret = ''; 
            for (var i = 0, len = minAry.length; i<len; i++) { 
                var srcNum = parseInt(minAry[i]); 
                var counter = 0; 
                for (var j = 0, ll = tAry.length; j<ll; j++) { 
                    var tt = tAry[j].split(","); 
                    for (var k = 0, l = tt.length; k<l; k++) { 
                        var tarNum = parseInt(tt[k]); 
                        if (srcNum == tarNum) { 
                            counter ++; 
                        } 
                    } 
                } 
                if (counter == tAry.length) { 
                    ret += srcNum + ","; 
                } 
            } 
            ret = strSlice(ret, ','); 
            alert("交集是：" + ret); 
        } 

        //去掉結尾分隔符 
        function strSlice(str, split){ 
            if ((str!=null && str!="") && (split!=' ')) 
                return ((str.charAt(str.length-1) == split) ? str.substring(0, str.length-1) : str); 
            else 
                return str; 
        } 
  </script> 

 </HEAD> 

 <BODY> 
    <button onclick="javascript:_test();">測試</button> 

    <select name="aa" id="aa" size="6" multiple> 
        <OPTION value="10004,10005,10008,10009,10010,10018">測試1</OPTION> 
        <OPTION value="10004,10005,10006,10008,10009,10010,10018">測試2</OPTION> 
        <OPTION value="10004,10005,10006,10008,10009,10010,10018">測試3</OPTION> 
        <OPTION value="10004,10006,10008">測試4</OPTION> 
        <OPTION value="10004,10010,10018">測試5</OPTION> 
    </select> 

 </BODY> 
</HTML> 