How to do queries in JSON

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const user = [
{
    "userid" : "1",
    "emailid" : "xyz@gmail.com",
    "password" : "xyz123",
    "cards" : [
        {
            "parentUId" : "1",
            "cardId" : "1A",
            "cardTitle" : "Buy Vegetables",
            "tasks" : [{
                "parentCId" : "1A",
                "taskId" : "1A1",
                "taskTitle" : "Tomato",
                "isCompleted" : false
            }, {
                "parentCId" : "1A",
                "taskId" : "1A2",
                "taskTitle" : "Onion",
                "isCompleted" : false
            }]
        },
        {
            "parentUId" : "1",
            "cardId" : "1B",
            "cardTitle" : "Buy Fruits",
            "tasks" : [{
                "parentCId" : "1B",
                "taskId" : "1B1",
                "taskTitle" : "Mango",
                "isCompleted" : false
            }, {
                "parentCId" : "1B",
                "taskId" : "1B2",
                "taskTitle" : "Apple",
                "isCompleted" : false
            }]
        }
    ]
},
{
    "userid" : "2",
    "emailid" : "abc@gmail.com",
    "password" : "abc123",
    "cards" : [
        {
            "parentUId" : "1",
            "cardId" : "2A",
            "cardTitle" : "Buy Vegetables",
            "tasks" : [{
                "parentCId" : "2A",
                "taskId" : "2A1",
                "taskTitle" : "Tomato",
                "isCompleted" : false
            }, {
                "parentCId" : "2A",
                "taskId" : "2A2",
                "taskTitle" : "Onion",
                "isCompleted" : false
            }]
        }
    ]
}
]

let uid = "2"
let cdTitle = "Buy Vegetables"


console.log(user[userid = uid].cards[cardTitle = cdTitle].tasks)

What I have tried:

It is showing error.
How to ask queries in json.
Any Good examples and exercises will be appreciated

Posted 4-Jan-23 22:56pm

shhhuuu

Updated 6-Jan-23 1:25am

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3 solutions

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Richard MacCutchan · Answer 1 · 2023-01-04T23:50:00

Solution 1

You probably need to convert the JSON to Javascript objects. See JavaScript JSON[^].

Posted 4-Jan-23 23:50pm

Richard MacCutchan

Sandeep Mewara · Answer 2 · 2023-01-04T23:51:00

Would suggest you too use an existing library that supports easy query into JSON data.

Couple of them:
NPM . json-query[^]
Simple Queries · JSONata[^]

Both the url's above have documentation/examples that will help you understand their usage.

With JSON-Query, following are the examples:

Queries are strings that describe an object or value to pluck out, or manipulate from the context object. The syntax is a little bit CSS, a little bit JS, but pretty powerful.
Accessing properties (dot notation)

person.name
Array accessors

people[0]
Array pluck

people.name => return all the names of people
Get all values of a lookup

lookup[*]
Array filter

By default only the first matching item will be returned:

people[name=Matt]

But if you add an asterisk (*), all matching items will be returned:

people[*country=NZ]

You can use comparative operators:

people[*rating>=3]

Or use boolean logic:

people[* rating >= 3 & starred = true]

If options.enableRegexp is enabled, you can use the ~ operator to match RegExp:

people[*name~/^R/i]

You can also negate any of the above examples by adding a ! before the = or ~:

people[*country!=NZ]
Or syntax

person.greetingName|person.name

Richard Deeming · Answer 3 · 2023-01-06T01:25:00

Quote:

JavaScript

user[userid = uid].cards[cardTitle = cdTitle].tasks

Firstly, the array indexer expects the index of the item to return. It does not accept an expression to match a specific item.

Secondly, you are using the assignment operator (=) to copy the existing variables (uid and cdTitle) to new previously-undefined variables (userid and cardTitle). That's not going to filter the items in any way.

You'll need to use a combination of filter[^] and flatMap[^] to perform your query. You'll also need to use optional chaining[^] to avoid an error if the item you're searching for doesn't exist.

JavaScript

const tasks = user.filter(u => u.userid === uid)?.flatMap(u => u.cards.filter(c => c.cardTitle === cdTitle))?.flatMap(c => c.tasks);
console.log(tasks);

How to do queries in JSON

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How to do queries in JSON

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