Package Exports

dynamodb-update-expression

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Readme

dynamodb-update-expression

A small library providing the solution to generate DynamoDB update expression by comparing the original data with update/remove JSON object.

Installation

npm install dynamodb-update-expression --save

Usage

var dynamodbUpdateExpression = require('dynamodb-update-expression');

var updateExpression = dynamodbUpdateExpression.getUpdateExpression(original, update);
var removeExpression = dynamodbUpdateExpression.getUpdateExpression(original, remove);

Where original, update, and remove should be a JSON object.

For example:

Original JSON:

var original = {
  "firstName": "John",
  "lastName": "Doe",
  "phones": [
        "1111-2222-333",
        "5555-4444-555"
    ],
  "family": [
    {
      "id": 1,
      "role": "father"
    }
    ],
  "profile": {
    "jobTitle": "Manager",
    "company": "ACME Inc",
    "business": {
      "license": "ABCD-123-LIC",
      "website": "www.acme.com"
    }
  }
};

Update JSON:

var updates = {
  "lastName": "L. Doe", // Will be updated
  // List of primitives
  "phones": [
        "1111-2222-333", // Original will be MERGED with this list
        "2222-4444-555"
    ],
  // List of object
  "family": [
    {
      "id": 2,
      "role": "mother"
    } // Original will be REPLACED by this (because of: deepmerge library bug)
    ],
  // Nested Object
  "profile": {
    "office": "1234 Market Street", // Add this element
    "business": {
      "website": "www.acmeinc.com", // Update this element
      "phone": "111222333" // Add this element
    },
    "company": "" // Remove this element because it is an empty string
  }
};

Remove JSON:

var removes = {
  "phones": [
        "1111-2222-333" // Will remove this number
    ],
  "profile": {
    "business": {
      "website": "www.acmeinc.com", // Will remove this element
      "phone": "111222333" // Won't be removed (not exists in original)
    }
  }
};

Output

Sample output

{
    "UpdateExpression": "SET #lastName = :lastName, #phones = :phones, #family = :family, #profilebusinesswebsite = :profilebusinesswebsite, #profilebusinessphone = :profilebusinessphone, #profileoffice = :profileoffice REMOVE #profilecompany",
    "ExpressionAttributeNames": {
        "#lastName": "lastName",
        "#phones": "phones",
        "#family": "family",
        "#profilebusinesswebsite": "profile.business.website",
        "#profilebusinessphone": "profile.business.phone",
        "#profileoffice": "profile.office",
        "#profilecompany": "profile.company"
    },
    "ExpressionAttributeValues": {
        ":lastName": "L. Doe",
        ":phones": [
            "1111-2222-333",
            "5555-4444-555",
            "2222-4444-555"
        ],
        ":family": [
            {
                "id": 2,
                "role": "mother"
            }
        ],
        ":profilebusinesswebsite": "www.acmeinc.com",
        ":profilebusinessphone": "111222333",
        ":profileoffice": "1234 Market Street"
    }
}

{
    "UpdateExpression": "REMOVE #family, #profile.#business.#website SET #phones = :phones",
    "ExpressionAttributeNames": {
        "#profile": "profile",
        "#business": "business",
        "#website": "website",
        "#family": "family",
        "#phones": "phones"
    },
    "ExpressionAttributeValues": {
        ":phones": [
            "5555-4444-555",
            "9999-8888-777"
        ]
    }
}

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