How to convert JSON object structure to dot notati

问题:

I've got a variable I'm storing that will dictate what fields to exclude from a query:

excludeFields = {
  Contact: {
    Address: 0,
    Phone: 0
  }
}

I need to convert this to a dot notation that will work with Mongo's findOne, e.g.:

things.findOne({}, {fields: {'Contact.Address': 0, 'Contact.Phone': 0}})

Just passing excludeFields does not work and results in an error, "Projection values should be one of 1, 0, true, or false"

things.findOne({}, {fields: excludeFields})

Do I have to write my own function to convert from hierarchical structure to flat dot notation? Or is there some mechanism to do this in JavaScript that I'm not aware of?

回答1:

This should be flexible enough for most needs:

function dotNotate(obj,target,prefix) {
  target = target || {},
  prefix = prefix || "";

  Object.keys(obj).forEach(function(key) {
    if ( typeof(obj[key]) === "object" ) {
      dotNotate(obj[key],target,prefix + key + ".");
    } else {
      return target[prefix + key] = obj[key];
    }
  });

  return target;
}

Run on your excludesFields variable like so:

dotNotate(excludeFields);

It returns the current structure:

{ "Contact.Address" : 0, "Contact.Phone" : 0 }

So you can even do, inline:

things.findOne({}, {fields: dotNotate(excludeFields) })

Or provide as a projection:

var projection = { "fields": {} };
dotNotate(excludeFields,projection.fields);
things.findOne({}, projection);

Works nicely at all depths and even with arrays in an essential way, unless you need operators like $push.

回答2:

I use a function pretty much similar to the accepted answer

    function convertJsonToDot(obj, parent = [], keyValue = {}) {
      for (let key in obj) {
        let keyPath = [...parent, key];
        if (obj[key]!== null && typeof obj[key] === 'object') {
            Object.assign(keyValue, convertJsonToDot(obj[key], keyPath, keyValue));
        } else {
            keyValue[keyPath.join('.')] = obj[key];
        }
    }
    return keyValue;
}

Here, I do an additional check 'obj[key] !== null' because unfortunately null is also of type 'object'.

I actually wanted to add this a comment to the accepted answer but couldn't because of not enough reputation.

回答3:

var fields = {};
for (var k in excludeFields) {
  for (var p in excludeFields[k]) {
    fields[k + '.' + p] = excludeFields[k][p];
  }
}

Then:

things.findOne({}, {fields: fields})