Javascript：如何通过在字符串中指定字段来创建对象？

Question

I'm trying to update a value in a MongoDB document. The document has many fields but I only want to specify a few of them depending on the fields I've changed in the UI.

var monthField='calendar.m'+month+'.result';
var triField='calendar.t'+trimester+'.result';
var yearField="calendar.year.result";

Objective.update({_id:{$in:objective.parents}},{
    $inc:
    {
        yearField:transaction.value,
        monthField:transaction.value,
        triField:transaction.value
    }},
    {multi:true, upsert:true}
  )

Unfortunately the above code does not "eval" the yearField , monthField and triField to their string values and instead is trying to update as if those fields exist in the document.

I know I can just find the documents, alter the values, and save them all one by one but is there a way to do what I'm trying to do? It's just so much better doing it in one update line.

Answer 1

Since you're using node.js, you can make use of computed property names , just by wrapping the names in brackets:

var monthField='calendar.m'+month+'.result';
var triField='calendar.t'+trimester+'.result';
var yearField="calendar.year.result";

Objective.update({_id:{$in:objective.parents}},{
    $inc:
    {
        [yearField]:transaction.value,
        [monthField]:transaction.value,
        [triField]:transaction.value
    }},
    {multi:true, upsert:true}
)

This syntax was added to the spec in ES2015, and while not ubiquitous yet, it is supported in node.js.