how to set key by var in mongoose,Node.js?

I don't set variable the key for update, my code...

mongoose.model('members', Schema).update({ id: '0' }, {$push: {'this_key': 'value'}} , [], function (err, data){});

if I use

var this_key = 'test';

but this_key is not 'test' it's 'this_key' in

    mongoose.model('members', Schema).update({ id: '0' }, {$push: {this_key: 'value'}} , [], function (err, data){});

I need get some value ext POST[] to set variable this_key,

how to set key by variable in mongoose,Node.js?

The syntax for string literals in object field names is biting you here. To get around it, make an intermediate object and construct it without using literals:

var this_key = 'test';
var push = {};
push[this_key] = 'value';   // here, it will use the variable

mongoose.model('members', Schema).update(
   { id: '0' }, {$push: push} , [], function (err, data){});