Session Storage Agent - JS/TS

Read and write value in session storage.

Logic Type	Available
Generic logic	✅
Aggregator logic	✅

Session Storage

For each executed task, a session storage is created in LOC runtime and shared by all logic in the same data process. It is the primary approach for a task to pass data from one lofic to others. The session storage will be purged after the task complete execution.

Import and Usage

JavaScript

import {
    SessionStorageAgent,
} from "@fstnetwork/loc-logic-sdk";

export async function run(ctx) {
    const data = await SessionStorageAgent.get("data");
}

export async function handleError(ctx, error) {
    // ... same
}

TypeScript

import {
    GenericContext,
    RailwayError,
    SessionStorageAgent,
} from "@fstnetwork/loc-logic-sdk";

export async function run(ctx: GenericContext) {
    const data = await SessionStorageAgent.get("data");
}

export async function handleError(ctx: GenericContext, error: RailwayError) {
    // ... same
}

Class Reference

Type

• SessionStorageAgent

Method: Get Session Value

async get(key: string): Promise<string | number | object | Uint8Array>

Parameter	Description
key	Key of session data

Returns a value from session storage (null if not exist).

The return type depends on how it was written into the session storage. If the value is a single number (which is valid JSON) and stored using putJson, it would be returned as a number.

Methods: Write Session Value

JSON

async putJson(key: string, value: any): Promise<boolean>

Parameter	Description
key	Key of session data
value	JavaScript JSON object

Write a JSON value into session storage. Overwrite if already exists.

warning

Runtime will throw a JSON parsing error if the object cannot be serialised properly to JSON.

You can try using JSON.parse(JSON.stringify(object) to transform an object with methods into a proper JSON object, although some fields may be different or discarded.

String

async putString(key: string, value: string): Promise<boolean>

Parameter	Description
key	Key of session data
value	string data

Write a string value into session storage. Overwrite if already exists.

Uint8Array

async putByteArray(key: string, value: Uint8Array | string): Promise<boolean>

Parameter	Description
key	Key of session data
value	Uint8Array or string data

Write a Uint8Array or string value into session storage. Overwrite if already exists.

Method: Delete Session Value

async delete(key: string): Promise<void>
async remove(key: string): Promise<void>

Parameter	Description
key	Key of session data

Delete a value in session storage. Do nothing if not exist.

Examples

Write String Data Into Session Storage

await SessionStorageAgent.putString(
    "data",
    "so long, and thanks for all the fish",
);

Write JSON Data Into Session Storage

await SessionStorageAgent.putJson("data", {
    name: "Arthur Dent",
    age: 42,
    job: {
        title: "Sandwich-maker",
        salary: 0,
    },
    quotes: [
        "Is there any tea on this spaceship?",
        "This must be Thursday. I never could get the hang of Thursdays.",
        "Would it save you a lot of time if I just gave up and went mad now?",
    ],
});

Write a Single Number

A single number is valid Json thus can be saved as a JSON session data:

await SessionStorageAgent.putJson("number", 42);

It will be read as a number from SessionStorageAgent.get.

tip

If the object contains methods, you can force convert it to a JSON object (although non-JSON values like undefined would be dropped):

await SessionStorageAgent.putJson(
    "data",
    JSON.parse(JSON.stringify(objectWithMethods)),
);

Read String Data from Session Storage

const data = await SessionStorageAgent.get("data");

Set a default value if the local data does not exist (returns null):

const data = await SessionStorageAgent.get("data") || "default value";

Read Json Data from Session Storage

const data = await SessionStorageAgent.get("data");

// get values (undefined if not found)
const name = data?.name;
const age = data?.age;
const title = data?.job?.title;

const quotes = data?.quotes;
const firstQuote = quotes ? quotes[0] : null;
for (const quote of quotes) {
    // ...
}