mongodb query field in object that is being edited - mongodb

Question

How can I query a field in an object? My html retrieves all the objects in array called 'postcards'
Meteor.user.profile.postcards [
{
_id: 84fh83f,
field_one: "a name",
field_two: " winter whether",
field_three: " lost more writing"
},
{
_id: 6jsf58s,
field_one: "another name",
field_two: " topical issues ",
field_three: " lost more writing"
}
]
Note: I used random.Id() so each object in the array can be uniquely identified.
Setting a session value to this._id when the user is focused on the input field will retrieve this unique id, however, I would like to query the actual field in focus. The value in these fields are projected within the text input area by using the spacebars syntax within the html.
Can I somehow assign the name within the curly braces of the value attribute to a variable? Then query?
Is there a whole new way to achieve this?
I want to update that specific field in this object instead updating the entire object.
HTML:
{{#with currentUser.profile}}
{{#each postcards}}
<input id="one" value="{{field_one}}" type="text">
<input id="two" value="{{field_two}}" type="text">
<input id="three" value="{{field_three}}" type="text">
{{/each}}
{{/with}}
client.js
Within events, I would like to update the field on focus upon keyup.
Templates.myTemplate.events({
'keyup input[type=text]': _.throttle(function(event) {
Meteor.users.update(this._id, {$set: {**fieldbeingedited**: event.target.value}});
}, 500);
});

Answer 1

What you want to have is an ES6 capability named 'Computed property names'.
This is what is looks like :
var x = 'hello',
obj = {
[x]: 'world'
};
console.log(obj); // Object {hello: "world"}
You have two options :
- you use the meteor harmony package to transpile your es6 to es5 (https://github.com/mquandalle/meteor-harmony)
- you build your object first
To build you object first :
var obj = {};
obj[ this.targetField ] = event.target.value
Meteor.users.update(this._id, {$set: obj});