Question

几天前，我发布了一个线程，询问如何在传递方法2 JS数组时找到缺少的元素。如您所见here。我一直在试图弄清楚如何修改方法，以便传递它而不是传递它2个数组2 2D-Arrays ...虽然有一些麻烦：

/*var sml = new Array();
sml[0] = new Array("dean","22");
sml[1] = new Array("james","31");
sml[2] = new Array("ludwig","35");

var lrg = new Array();
lrg[0] = new Array("dean","22");
lrg[1] = new Array("james","31");
lrg[2] = new Array("ludwig","35");
lrg[3] = new Array("kevin","23");
lrg[4] = new Array("elton","40");*/

var sml = new Array();
sml[0] = "dean";
sml[1] = "james";
sml[2] = "ludwig";

var lrg = new Array();
lrg[0] = "dean";
lrg[1] = "james";
lrg[2] = "ludwig";
lrg[3] = "kevin";
lrg[4] = "elton";


var deselected = findDeselectedItem(sml, lrg);

alert("Deselected Items: " + deselected[0]+", "+ deselected[1]);

// -------------------------------------------------------------- //

function findDeselectedItem(CurrentArray, PreviousArray) {


var CurrentArrSize = CurrentArray.length;
var PreviousArrSize = PreviousArray.length;
var deselectedItems = new Array();

// loop through previous array
for (var j = 0; j < PreviousArrSize; j++) {

    // look for same thing in new array
    if (CurrentArray.indexOf(PreviousArray[j]) == -1)

    deselectedItems.push(PreviousArray[j]);

}

if (deselectedItems.length != 0) {
    return deselectedItems;
} else {
    return null;
}

}

现在，如果你运行上面的代码它可以很好地工作，但是如果你去取消注释顶部的变量声明，那就是将数组推到数组的顶部，然后注释掉被推到数组顶部的简单字符串，它不起作用......例如：

var sml = new Array();
sml[0] = new Array("dean","22");
sml[1] = new Array("james","31");
sml[2] = new Array("ludwig","35");

var lrg = new Array();
lrg[0] = new Array("dean","22");
lrg[1] = new Array("james","31");
lrg[2] = new Array("ludwig","35");
lrg[3] = new Array("kevin","23");
lrg[4] = new Array("elton","40");

/*var sml = new Array();
sml[0] = "dean";
sml[1] = "james";
sml[2] = "ludwig";

var lrg = new Array();
lrg[0] = "dean";
lrg[1] = "james";
lrg[2] = "ludwig";
lrg[3] = "kevin";
lrg[4] = "elton";*/


var deselected = findDeselectedItem(sml, lrg);

alert("Deselected Items: " + deselected[0]+", "+ deselected[1]);

// -------------------------------------------------------------- //

function findDeselectedItem(CurrentArray, PreviousArray) {


var CurrentArrSize = CurrentArray.length;
var PreviousArrSize = PreviousArray.length;
var deselectedItems = new Array();

// loop through previous array
for (var j = 0; j < PreviousArrSize; j++) {

    // look for same thing in new array
    if (CurrentArray.indexOf(PreviousArray[j][0]) == -1)

    deselectedItems.push(PreviousArray[j][0]);

}

if (deselectedItems.length != 0) {
    return deselectedItems;
} else {
    return null;
}

}

该方法返回2个完全错误的值。 PS - 我对“数字”不感兴趣，现在只是“名字”......

Answer 1

您的CurrentArray是2维的，indexOf会比较数组，但不会比较该数组的第一个元素。所以你需要使用：

for ( var i = 0; i < CurrentArray.length; ++i){
    if (CurrentArray[i][0] == PreviousArray[j][0]){
        deselectedItems.push(PreviousArray[j][0]);
        break;
    }
}

而不是

if (CurrentArray.indexOf(PreviousArray[j][0]) == -1)
    deselectedItems.push(PreviousArray[j][0]);

Answer 2

在这种情况下，

indexOf函数将检查对象相等性;要使它返回除-1以外的其他东西，你必须将相同的2D数组实例传递给sml和lrg。

new Array("dean","22") === new Array("dean","22") //false

在两个数组中保持相同的实例（例如http://jsfiddle.net/3TQYz/）或使用您自己的indexOf测试，该测试会递归检查数组的值以使您的案例正常工作。

Answer 3

您也可以像这样重新排列数组：

var sml = {};
sml["dean"] = 22;
sml["james"] = 31;
sml["ludwig"] = 35;

var lrg = {};
lrg["dean"] = 22;
lrg["james"] = 31;
lrg["ludwig"] = 35;
lrg["kevin"] = 23;
lrg["elton"] = 40;

并使用：

function findDeselectedItem(c,p){
    ret=[];
    for (var i in p){
        if (p.hasOwnProperty(i)){
            if ('undefined'===typeof c[i]) {
                ret.push(i);
            }
        }
    }
    return ret;
}


alert(findDeselectedItem(sml, lrg));

演示：http://jsfiddle.net/LsrCj/

通过比较Javascript中的2个2D数组来查找缺少的元素

3 个答案: