You can update any json object with this code below.

Update object in dynamodb

const object = {
    "name": "blabla",
    "surname": "blabla",
    "age": 18,
    "foo": "bar",
    "date": new Date().toString()
};

var updatedKeys = Object.keys(object);
/**
 * it returns the update expression for dynamodb.
 * example:
 * "set name = :name, surname = :surname, age = :age, foo = :foo, date = :date"
 * @type {string}
 */
var updateExpression = "set " + updatedKeys.map(x => `${x} = :${x}`).join(", ");

var expressionAttributeValues = {};
/**
 * it fills :key with the value in dynamodb format.
 * example:
 * expressionAttributeValues = {
    ":name": "blabla",
    ":surname": "blabla",
    ":age": 18,
    ":foo": "bar",
    ":date": new Date().toString()
 * }
 */
updatedKeys.forEach((key) => expressionAttributeValues[`:${key}`] = object[key])
let params = {
    TableName: TABLE_NAME,
    Key: {
        "pk": `your_pk`,
        "sk": `your_sort_key_if_exists`
    },
    UpdateExpression: updateExpression,
    ExpressionAttributeValues: expressionAttributeValues
}