Mongodb scripting Positional operator

Question

I am looking at updating array objects in mongodb documents as below

var cursor = db.coll.find();
cursor.forEach(function(x){
  if(x.arr) {
    x.arr.forEach(function(y,i){
      if(y.field1) {
        db.coll.update({_id: x._id}, {$set:{'arr.'+i+'.field1': 'x' + y.field1}})
      }
    })
  }
})

I get a syntax error at {$set:{'arr.'+i+'.field1': 'x' + y.field1}} Is there a workaround?

hyades · Accepted Answer · 2017-02-07 17:46:30Z

1

You are trying to dynamically assign values to the key of JavaScript object at the initialization time. Just create it separately and assign the key at a later step.

var cursor = db.coll.find();
cursor.forEach(function(x){
  if(x.arr) {
    x.arr.forEach(function(y,i){
      if(y.field1) {
        var setStmt = {};
        setStmt['arr.'+i+'.field1'] = 'x' + y.field1;
        db.coll.update({_id: x._id}, {$set: setStmt});
      }
    })
  }
})

answered Feb 7, 2017 at 17:46

hyades

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