Initiate a template iteration in Meteor - meteor

Question

Rather than loading a new template, is there a way to force Meteor to initiate an iteration (using {{#each}}) of an array in Meteor? For example, if the user selects a value in a pull down selector, to then initiate Meteor to iterate through an array within that template to populate another multiple selector list rather than load a whole new template with the new selector list.
Let's say this is within a template:
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<form class="input-field col s6 card-selector">
<select multiple">
<option value="" disabled selected>Select Students</option>
{{#each StudentList1}}
<option value= '{{FullName}}'>{{formatName FullName}} ({{Level}}) {{RoomWk1}}</option>
{{/each}}
</select>
</form>
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.
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When a user selects a value in a different selector in that template:
<select class="week-selector">
<option value="" disabled selected>Week</option>
<option value="Week1">Week 1</option>
<option value="Week2">Week 2</option>
<option value="Week3">Week 3</option>
<option value="Week4">Week 4</option>
<option value="Week5">Week 5</option>
</select>
it will force a reiteration of the first #each to:
<form class="input-field col s6 card-selector">
<select multiple">
<option value="" disabled selected>Select Students</option>
{{#each StudentList1}}
<option value= '{{FullName}}'>{{formatName FullName}} ({{Level}}) {{RoomWk2}}</option>
{{/each}}
</select>
</form>
It would be more efficient than loading a new template that's the same except for the multi selector values.

Answer 1

Sessions are reactive and you can achieve this by using sessions (check if you have session package).
//we don't want the session value from the previous search/events
Template.templateName.onRendered(function(){
Session.set('sessionName', undefined);
});
//I'd probably use onDestroyed instead of onRendered
Template.templateName.onDestroyed(function(){
Session.set('sessionName', undefined);
});
//template events
'change .week-selector': function(){
var selected = $('.week-selector').find(":selected").text();
Session.set('sessionName', selected)
}
//template helper
StudentList1: function(){
var session = Session.get('sessionName');
if(session !== undefined){
//return some documents using the session value in your find()
} else {
//return documents without session value
}
}
EDIT: I found .text() of the selected option in the event but you are free to return value or do whatever you want with the found value/text.