javascript Meteor - 在选择更改时更新 var
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Meteor - update var on select change
提问by Kobus Post
I've got a dropdown, but when a user select another value, I want some code to be executed. My question: How can I check whether the selected value of the dropdown has changed?
我有一个下拉列表，但是当用户选择另一个值时，我希望执行一些代码。我的问题：如何检查下拉列表的选定值是否已更改？
In my html file:
在我的 html 文件中：
<template name="jaren">
<form id="yearFilter">
<select class="selectpicker span2" id="yearpicker" >
{{#each jaren}}
{{#if selectedYear}}
<option selected value="{{_id}}">{{jaar}} {{description}}</option>
{{else}}
<option value="{{_id}}">{{jaar}} {{description}}</option>
{{/if}}
{{/each}}
</select>
</form>
</template>
in my javascript file:
在我的 javascript 文件中：
Template.jaren.jaren = function() {
return Years.find();
}
Template.jaren.selectedYear = function() {
if (Session.get('year_id') == this._id) {
return true;
} else {
return false;
}
}
Template.jaren.events({
'change form#yearFilter #yearpicker': function(event, template) {
Session.set('year_id', template.find('#yearpicker').value);
console.log("value changed");
}
});
回答by Rahul
You can get the value of the select element inside the event handler and then compare it to the old value you had already stored:
您可以在事件处理程序中获取 select 元素的值，然后将其与您已经存储的旧值进行比较：
"change #yearpicker": function(evt) {
var newValue = $(evt.target).val();
var oldValue = Session.get("year_id");
if (newValue != oldValue) {
// value changed, let's do something
}
Session.set("year_id", newValue);
}
回答by Daniel Budick
A solution with pure JavaScript would be:
使用纯 JavaScript 的解决方案是：
'change #yearpicker': function (event) {
var currentTarget = event.currentTarget;
var newValue = currentTarget.options[currentTarget.selectedIndex].value;
if(!Session.equals('year_id', newValue)){
Session.set('year_id', newValue);
}
}
