Lodash remove items recursively

There doesn't seem to be a deep omit, but you could iterate over all the keys in the object, and delete reach from the nested objects, recursively:

function omitDeep(obj) {
  _.forIn(obj, function(value, key) {
    if (_.isObject(value)) {
      omitDeep(value);
    } else if (key === 'reach') {
      delete obj[key];
    }
  });
}

var obj = { 
  total: 350,
  SN1: { 
    reach: 200,
    engagementRate: 1.35
  },
  SN2: {
    reach: 150,
    engagementRate: 1.19
  }
};

function omitDeep(obj) {
  _.forIn(obj, function(value, key) {
    if (_.isObject(value)) {
      omitDeep(value);
    } else if (key === 'reach') {
      delete obj[key];
    }
  });
}
omitDeep(obj)
console.log(obj);
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_.transform() the object to another object, and while passing the values to the new object, check if the value is an object and if it has the 'reach' property, and if so use _.omit() to get a new object without reach:

var obj = {
  total: 350,
  SN1: {
    reach: 200,
    engagementRate: 1.35
  },
  SN2: {
    reach: 150,
    engagementRate: 1.19
  }
};

var result = _.transform(obj, function(result, value, key) {
  result[key] = _.isObject(value) && `reach` in value ? _.omit(value, 'reach') : value;
});

console.log(result);
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And if you need a recursive solution that will handle multiple nested object levels, here is deepOmit, which uses the same idea, but without _.omit, and can be used to remove multiple keys (see comments in code):

var obj = {
  total: 350,
  SN1: {
    reach: 200,
    engagementRate: 1.35,
    DEEP_SN1: {
      reach: 200,
      engagementRate: 1.35
    }
  },
  SN2: {
    reach: 150,
    engagementRate: 1.19
  }
};

function deepOmit(obj, keysToOmit) {
  var keysToOmitIndex =  _.keyBy(Array.isArray(keysToOmit) ? keysToOmit : [keysToOmit] ); // create an index object of the keys that should be omitted

  function omitFromObject(obj) { // the inner function which will be called recursivley
    return _.transform(obj, function(result, value, key) { // transform to a new object
      if (key in keysToOmitIndex) { // if the key is in the index skip it
        return;
      }

      result[key] = _.isObject(value) ? omitFromObject(value) : value; // if the key is an object run it through the inner function - omitFromObject
    })
  }
  
  return omitFromObject(obj); // return the inner function result
}

console.log(deepOmit(obj, 'reach')); // you can use a string for a single value

console.log(deepOmit(obj, ['reach', 'engagementRate'])); // you can use an array of strings for multiple values
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