几个小时以来我一直在尝试自己解决这个问题,现在我举手看看是否有人有任何想法。
问题
我正在制作一个动态侧边栏过滤器,它迭代 groups
属性并返回带有查询属性的 Link
来更新路由器。将显示一个复选框,并根据当前是否排除该组 ID 进行标记。
代码
render: function() {
return (
<ul>
{this.props.query.filter == 'connections' ?
// the array of groups to build the filter for
this.props.groups.map(function (group) {
// this array would start with the currently excluded ids, and end with the new list of ids
var new_ids = this.context.router.getCurrentQuery().exclude || [];
var index = new_ids.indexOf(group.id.toString());
console.log('my id: ' + group.id);
console.log('starting: ' + new_ids);
// again, the array is excluded ids, so if it's not in the array it should be checked
var selected = index == -1;
if (selected) {
// if this link is clicked, add the id to the excludes
new_ids.push(group.id);
}
else {
// if this linked is clicked, remove the id from the excludes
new_ids.splice(index, 1);
}
console.log('ending: '+new_ids);
// return the preloaded link
return <Link key={group.name}
to="feed"
query={{filter: 'connections', exclude: new_ids}}>
<small>{group.name}</small>
</Link>;
}, this) : null }
</ul>
);
当我使用 input type="checkbox"
和带有 this.transitionTo
的事件处理程序时,这有效,但我想使用 Link
code> 组件来处理请求而不是事件处理程序。
结果
该页面在第一次点击时工作正常(query.exclude == undefined
),但之后 new_ids
会随着每次迭代而发生变化。
这是控制台输出...
id: 11
starting:
new ids: 11
id: 6
starting:
new ids: 6
id: 21
starting:
new ids: 21
单击其中一个后(例如第一组 - id 11,它会困惑)...
id: 11
starting: 11
new ids: // this is correct, it removes 11 from the list
id: 6
starting: // this should be 11, instead its inheriting the prior value
new ids: 6 // this should be 11, 6
id: 21
starting: 6 // this should be 11, instead its inheriting the prior value
new ids: 6,21 // this should be 11, 21
我尝试将此迭代设为 for ... 循环
而不是 .map()
但这没有帮助。我还将最初的 excepted_ids 移出迭代,但结果又相同。
同样,这一切应该做的就是根据单击链接的结果生成用于导航的 query.exclude
属性的值。
任何有关可能发生的事情的想法将不胜感激。谢谢。
最佳答案
以下是避免改变 exclude
数组的方法。
render: function() {
return (
<ul>
{this.props.query.filter == 'connections' ?
// the array of groups to build the filter for
this.props.groups.map(function (group) {
// this array would start with the currently excluded ids, and end with the new list of ids
var new_ids = this.context.router.getCurrentQuery().exclude || [];
console.log('my id: ' + group.id);
console.log('starting: ' + new_ids);
var found = false;
new_ids = new_ids.filter(function(exclude){
if(exclude != group.id.toString()){
return true;
} else {
found = true;
return false;
}
});
if(!found) {
new_ids.push(group.id);
}
//new_ids now has a copy of the exclude array with the values excluded.
console.log('ending: '+new_ids);
// return the preloaded link
return <Link key={group.name}
to="feed"
query={{filter: 'connections', exclude: new_ids}}>
<small>{group.name}</small>
</Link>;
}, this) : null }
</ul>
);
Array.prototype.filter
基本上遍历数组并检查每个元素。如果返回值为true
,它将添加到新数组,否则正在迭代的元素将被丢弃。
这是一个以类似方式工作的非 react 脚本。
var group = [1,2,3,4,5,6,7,8,9,10,11];
var excluded = [11];
var results = document.getElementById('results');
group.forEach(function(group){
var new_ids = excluded;
results.innerHTML += 'my id: ' + group + '\n';
results.innerHTML += 'starting: ' + new_ids + '\n';
var found = false;
new_ids = new_ids.filter(function(exclude){
if(exclude != group){
return true;
} else {
found = true;
return false;
}
});
if(!found){
new_ids.push(group);
}
results.innerHTML += 'ending: ' + new_ids + '\n';
});
<pre id="results"></pre>
关于javascript - 循环内声明的变量保留先前的值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32230875/