JS: Local database, transport and token helpers

Local database, transport and token helpers¶

Source code: src/helpers.js

jdb, a small database in memory¶

A jdb is a JSON object with a schema, a set of topics and a hook name. It holds the records of a view while the page is open. It is not TreeDB, which is the graph database of the backend.

{
    hook:   "data",
    type:   [],
    schema: { app_menu: [], account_menu: [], … },
    topics: { app_menu: [ {id: …}, … ] }
}

A record is written under another one by the path of ids that leads to it, and it goes in the hook list of its parent. Writing an id that is already there updates it:

const jdb = jdb_init({schema: {menu: []}});      // topics: {menu: []}, hook "data"
jdb_update(jdb, "menu", "", {id: "home", label: "Home"});
jdb_update(jdb, "menu", "home", {id: "users", label: "Users"});
jdb_update(jdb, "menu", "home", {id: "users", label: "People"});   // updated
// jdb.topics.menu:
//     [{id: "home", label: "Home", data: [{id: "users", label: "People"}]}]
jdb_delete(jdb, "menu", "home", {id: "users"});
jdb_get(jdb, "menu", "home");    // {id: "home", label: "Home", data: []}

Before gobj-js 7.26.9, jdb_init() created no topic and no hook.

jdb_init(jdb, prefix, duplicate)¶

Prepares a jdb, and builds one topic for each LEAF of the schema: a key whose value is a dict groups topics, it is not one ({a: {b: [], c: []}} gives the topics a`b and a`c; since 7.26.10). An empty dict is an empty group: {a: {}} gives no topic at all. With duplicate set to true the function works on a deep copy, and the caller keeps its own object. It gives the jdb back.

A key of the schema that begins with two underscores is metadata, and the function builds no topic for it.

jdb_update(jdb, topic_name, path, kw)¶

Writes a record in a topic, and gives the topic back. A record whose id is already in the list it goes in is updated, at the root too (since gobj-js 7.26.11; at the root it was added a second time). The function returns null and writes a log error when the topic does not exist, when the record has no id, when path is not a string (since 7.26.8; it threw before), when a record of path is not there (since 7.26.10; it gave the topic back as if it had written), or when the hook of the record path ends on is not a list (since 7.26.11; it threw), when the record is not an object, or when path has an empty segment ("a`"; since 7.26.12, it threw or was taken as "a"). An update that fails leaves the jdb as it was.

jdb_update(jdb, "menu", "home`nope", {id: "x"});   // null, logged: no "nope" under "home"

jdb_delete(jdb, topic_name, path, kw)¶

Deletes a record from a topic, and gives the topic back. It returns null with a log error in the same cases as jdb_update(), and when the record to delete is not there (since 7.26.10).

jdb_delete(jdb, "menu", "home", {id: "nope"});     // null, logged: nothing to delete

jdb_get(jdb, topic_name, id, recursive)¶

Gives the record with an identifier. The search goes down into the children through the hook. With recursive not given the function goes down.

jdb_get_by_idx(jdb, topic_name, idx)¶

Gives the record at an index of a topic.

jdb_get_topic(jdb, topic_name)¶

Gives a whole topic. Returns null and writes a log error when the topic does not exist.

Files and HTTP¶

load_json_file(url, on_success, on_error)¶

Reads a JSON file from a URL, and calls on_success with the object. It calls on_error when the read fails.

send_http_json_post(url, data, on_response)¶

Sends a POST request with a JSON body. It calls on_response(status, response_data).

Tokens¶

jwtDecode(jwt)¶

Reads a JWT, and gives its three parts back.

jwt2json(jwt, what)¶

Reads one part of a JWT as JSON. what accepts "header", "payload" and "signature", and the default is "payload".