我有两个数组。每个数组的元素如下所示：
allLabBranches = [{
"labbranchid": "1",
"labname": "Wahab Labs, Islampura Branch, Lahore",
"labtitle": "Wahab Labs Lahore",
"shortname": "WAHB",
"address": "56 Islampura, Lahore",
"landlineno": "04237940445",
"datecreated": "2016-03-11 11:00:00",
"createdbyname": "Jamshaid Sabir",
"createdbyuserid": "1",
"dateupdated": "2016-05-04 00:53:03",
"updatedbyname": "Jamshaid Sabir",
"updatedbyuserid": "1",
"clientgroups_clientgroupsid": "1",
"startdate": "2016-05-04"
}, {
"labbranchid": "2",
"labname": "Wahab Labs, Model Town Branch, Lahore",
"labtitle": "Wahab Labs Lahore",
"shortname": "WAHAB",
"address": "45 Model Town, Lahore",
"landlineno": "04237945485",
"datecreated": "2016-03-11 11:00:00",
"createdbyname": "Jamshaid Sabir",
"createdbyuserid": "1",
"dateupdated": "0000-00-00 00:00:00",
"updatedbyname": "",
"updatedbyuserid": "",
"clientgroups_clientgroupsid": "1",
"startdate": "0000-00-00"
}, {
"labbranchid": "3",
"labname": "Shahdara More Branch",
"labtitle": "Wahab Labs Lahore",
"shortname": "WAHAB",
"address": "Shahdara",
"landlineno": "04237933415",
"datecreated": "2016-03-11 11:48:15",
"createdbyname": "Jamshaid Sabir",
"createdbyuserid": "1",
"dateupdated": "0000-00-00 00:00:00",
"updatedbyname": "",
"updatedbyuserid": "",
"clientgroups_clientgroupsid": "1",
"startdate": "0000-00-00"
}, {
"labbranchid": "4",
"labname": "New Branch",
"labtitle": "Wahab Labs Lahore",
"shortname": "WAHB",
"address": "More Samanabad, Lahore",
"landlineno": "042361561",
"datecreated": "2016-03-11 11:52:06",
"createdbyname": "Jamshaid Sabir",
"createdbyuserid": "1",
"dateupdated": "2016-03-14 15:06:44",
"updatedbyname": "Jamshaid Sabir",
"updatedbyuserid": "1",
"clientgroups_clientgroupsid": "1",
"startdate": "2016-03-14"
}, {
"labbranchid": "5",
"labname": "Test Branch",
"labtitle": "xyz",
"shortname": "sfwe",
"address": "dsfasd",
"landlineno": "sdfasd",
"datecreated": "2016-03-12 00:14:11",
"createdbyname": "Jamshaid Sabir",
"createdbyuserid": "1",
"dateupdated": "2016-08-11 12:54:12",
"updatedbyname": "Jamshaid Sabir",
"updatedbyuserid": "1",
"clientgroups_clientgroupsid": "1",
"startdate": "2016-03-12"
}, {
"labbranchid": "6",
"labname": "Test Branch 2",
"labtitle": "asdfs",
"shortname": "asdfs",
"address": "asdf",
"landlineno": "asdf",
"datecreated": "2016-03-12 12:16:24",
"createdbyname": "Jamshaid Sabir",
"createdbyuserid": "1",
"dateupdated": "0000-00-00 00:00:00",
"updatedbyname": "",
"updatedbyuserid": "",
"clientgroups_clientgroupsid": "1",
"startdate": "2016-03-12"
}, {
"labbranchid": "7",
"labname": "Wahab Labs, Shahdara Branch, Lahore",
"labtitle": "Shahdara",
"shortname": "Shahdara",
"address": "Shahdara",
"landlineno": "0423744915",
"datecreated": "2016-08-11 12:56:27",
"createdbyname": "Jamshaid Sabir",
"createdbyuserid": "1",
"dateupdated": "2016-08-11 12:57:01",
"updatedbyname": "Jamshaid Sabir",
"updatedbyuserid": "1",
"clientgroups_clientgroupsid": "1",
"startdate": "2016-08-01"
}]
另一个数组元素是：
labsOfUser = [{
"userhasbranchid": "53",
"labbranches_labbranchid": "6",
"usersoflabs_userId": "9"
}, {
"userhasbranchid": "54",
"labbranches_labbranchid": "1",
"usersoflabs_userId": "9"
}, {
"userhasbranchid": "55",
"labbranches_labbranchid": "7",
"usersoflabs_userId": "9"
}, {
"userhasbranchid": "56",
"labbranches_labbranchid": "2",
"usersoflabs_userId": "9"
}]
现在我有一个选择多个框，我显示一些分支为选中，一些分支未选中。代码如下：
function populateSelectedLabs() {
$('#labbranchids').empty();
if (allLabBranches.length >= labsOfUser.length) {
for (var i = 0; i < allLabBranches.length; i++) {
for (var j = 0; j < labsOfUser.length; j++) {
if (allLabBranches[i].labbranchid == labsOfUser[j].labbranches_labbranchid) {
$("#labbranchids").append("<option selected='selected' value='" + allLabBranches[i].labbranchid + "'>" + allLabBranches[i].labname + "</option>");
allLabBranches = jQuery.grep(allLabBranches, function(value) {
return value != allLabBranches[i];
});
} //end inner if
} //end inner loop
} //end outer loop
} //end if
for (var i = 0; i < allLabBranches.length; i++) {
$("#labbranchids").append("<option value='" + allLabBranches[i].labbranchid + "'>" + allLabBranches[i].labname + "</option>");
} //end for loop
} //end function
问题是数组元素比较错过了一个元素，该元素存在于数组中但位于数组中的不同索引处。错误发生在以下代码行：
if(allLabBranches[i].labbranchid == labsOfUser[j].labbranches_labbranchid){
请帮助我知道如何比较两个阵列中的所有元素？
答案 0 :(得分：1)
某些项目不匹配的原因是您在同一阵列上重新定义循环内的allLabBranches，使其更短。
我们假设在更改之前，以下情况属实：
labsOfUser[j-1].labbranches_labbranchid == allLabBranches[i+1].labbranchid
您可能希望稍后在外部循环的下一次迭代中检测到此相等性。但由于重新分配到allLabBranches，此值不再是索引i+1，而是i。在内循环的剩余部分期间，该值将不再匹配（因为匹配值在j-1），因此i将在外循环的下一次迭代中递增。因此，这个值永远不会匹配。
您可以通过向后迭代allLabBranches数组来解决此问题，但更好的方法是使用labsOfUser数组中的值创建哈希值。这将有更好的表现。
你可以这样做：
function populateSelectedLabs() {
$('#labbranchids').empty();
// create hash
var hash = {};
for (var j = 0; j < labsOfUser.length; j++) {
hash[labsOfUser[j].labbranches_labbranchid] = 1;
}
allLabBranches = jQuery.grep(allLabBranches, function(value) {
return hash[value.labbranchid];
}).concat(jQuery.grep(allLabBranches, function(value) {
return !hash[value.labbranchid];
}));
for (var i = 0; i < allLabBranches.length; i++) {
$("#labbranchids").append($('<option>')
.val(allLabBranches[i].labbranchid)
.text(allLabBranches[i].labname)
.attr('selected', hash[allLabBranches[i].labbranchid]));
}
}
如果目标浏览器支持ES6，那么您可以这样写：
function populateSelectedLabs() {
$('#labbranchids').empty();
var hash = new Set(labsOfUser.map( value => value.labbranches_labbranchid ));
allLabBranches.filter( value => hash.has(value.labbranchid) )
.concat(allLabBranches.filter( value => !hash.has(value.labbranchid) ))
.forEach( value =>
$("#labbranchids").append($('<option>')
.val(value.labbranchid)
.text(value.labname)
.attr('selected', hash.has(value.labbranchid)))
);
}