A guide on inserting an element into a serialized linked list using Javascript

Question

A guide on inserting an element into a serialized linked list using Javascript

Suppose I serialize a linked list into JSON format and save it in a text file

const myList = new SinglyLinkedList();
myList.push('Bonjour');
myList.push('Monde');
myList.push('!');
myList.print();

fs.writeFile('./test.txt', JSON.stringify(myList), err => {
    if (err) {
        console.log(err);
        return;
    }
})

After reading the file and de-serializing the data, how can I add a new element to this linked list and re-serialize it?

Serialization only retains the object's state, so is there a way to update the list with a new element and serialize it again?

javascript json serialization data-structures linked-list

Answer 1

Answer №1

JSON.parse has limitations in terms of the data types it can produce, including boolean, number, string, null, array, and plain object. It cannot generate instances of custom classes.

To address this issue, here are some suggestions:

There is no need to serialize the next references in a linked list since their order implicitly defines these links.
You can serialize a linked list as if it were an array.
Implement iterable linked list instances to easily convert them into arrays for serialization.
Create a toJSON method that will be called by JSON.stringify.
Allow the linked list constructor to accept multiple arguments that are immediately added to the new list, similar to how the Array constructor works.
Add a static method fromJSON to create a linked list instance from a JSON string.

This implementation demonstrates the above points:

class SinglyLinkedList {
    static Node = class {
        constructor(value, next=null) {
            this.value = value;
            this.next = next;
        }
    }
    constructor(...values) {
        this.head = this.tail = null;
        for (let value of values) this.push(value);
    }
    push(value) {
        let node = new SinglyLinkedList.Node(value);
        if (this.tail) {
            this.tail = this.tail.next = node;
        } else {
            this.head = this.tail = node;
        }
    }
    * [Symbol.iterator]() {
        for (let node = this.head; node; node = node.next) {
            yield node.value;
        }
    }
    toJSON() {
        return [...this];
    }
    static fromJSON(json) {
        return new this(...JSON.parse(json));
    }
}

// Demo
// 1. Constructor can accept values to be added to the list
const list = new SinglyLinkedList('Hello', 'World', '!');

// 2. A linked list can be iterated, so no specific print method is needed
console.log(...list);

// 3. JSON.stringify will call toJSON method
let serialized = JSON.stringify(list);
console.log(serialized);

// 4. fromJSON can be used to create a linked list instance from Array-like JSON
let restored = SinglyLinkedList.fromJSON(serialized);

// Again, iteration can be used for printing
console.log(...restored);

Answer 2

JSON.parse has limitations in terms of the data types it can produce, including boolean, number, string, null, array, and plain object. It cannot generate instances of custom classes.

To address this issue, here are some suggestions:

There is no need to serialize the next references in a linked list since their order implicitly defines these links.
You can serialize a linked list as if it were an array.
Implement iterable linked list instances to easily convert them into arrays for serialization.
Create a toJSON method that will be called by JSON.stringify.
Allow the linked list constructor to accept multiple arguments that are immediately added to the new list, similar to how the Array constructor works.
Add a static method fromJSON to create a linked list instance from a JSON string.

This implementation demonstrates the above points:

class SinglyLinkedList {
    static Node = class {
        constructor(value, next=null) {
            this.value = value;
            this.next = next;
        }
    }
    constructor(...values) {
        this.head = this.tail = null;
        for (let value of values) this.push(value);
    }
    push(value) {
        let node = new SinglyLinkedList.Node(value);
        if (this.tail) {
            this.tail = this.tail.next = node;
        } else {
            this.head = this.tail = node;
        }
    }
    * [Symbol.iterator]() {
        for (let node = this.head; node; node = node.next) {
            yield node.value;
        }
    }
    toJSON() {
        return [...this];
    }
    static fromJSON(json) {
        return new this(...JSON.parse(json));
    }
}

// Demo
// 1. Constructor can accept values to be added to the list
const list = new SinglyLinkedList('Hello', 'World', '!');

// 2. A linked list can be iterated, so no specific print method is needed
console.log(...list);

// 3. JSON.stringify will call toJSON method
let serialized = JSON.stringify(list);
console.log(serialized);

// 4. fromJSON can be used to create a linked list instance from Array-like JSON
let restored = SinglyLinkedList.fromJSON(serialized);

// Again, iteration can be used for printing
console.log(...restored);

A guide on inserting an element into a serialized linked list using Javascript

Answer №1

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