I need to convert a Symbol to string in order to create a unique key in Redis, but I can't.
I've already tried to use Object.toString(obj) and String(obj) but I get errors or [Object] results¡.
This is the controller
const name = req.params.name;
let obj;
obj.data.name = {
[Op.like]: '%' + name + '%'
};
}
This is redis controller where I use stringify. I use obj as a parameter.
const hashed = crypto.createHmac('sha256', secretHashKey)
.update(JSON.stringify(obj))
.digest('hex');
I expect an output based on my parameter 'obj' but now it's not getting it so I can't create unique keys for different values.
Maybe a little bit too late, but I hope that somebody else find this useful.
I was looking for something exactly as you: use with Sequelize in a Redis cache.
Mine is TypeScript, convert to JavaScript just by removing the typings.
export function JsonStringifyWithSymbols(object: any, clean?: boolean): string {
return JSON.stringify(object, (_, value) => {
if (typeof value === 'object' && !Array.isArray(value) && value !== null) {
const props = [...Object.getOwnPropertyNames(value), ...Object.getOwnPropertySymbols(value)];
const replacement: Record<string, any> = {};
for (const k of props) {
if (typeof k === 'symbol') {
replacement[`Symbol:${Symbol.keyFor(k)}`] = value[k];
} else {
replacement[k] = value[k];
}
}
return replacement;
}
return value;
});
}
If you're meaning these Symbols you can't convert them to a string.
They're created to be unique and "unreversable", so you can use them also for keep more "secure" various properties or methods. Example:
const a = Symbol('a')
class Foobar {
constructor (_a) {
this[a] = _a
}
}
const foobar = new Foobar('aaa')
console.log(foobar) // output: Foobar { [Symbol(a)]: 'aaa' }
const fake = Symbol('a')
foobar[fake] = 'fake'
console.log(foobar) // output: Foobar { [Symbol(a)]: 'aaa', [Symbol(a)]: 'fake' }
You can't corrupt the original one, unless you have the original Symbol.
Another example (info about the JSON.stringify here):
const a = Symbol('a')
const foobar = {}
foobar[a] = 'aaa'
console.log(foobar) // output: { [Symbol(a)]: 'aaa' }
console.log(JSON.stringify(foobar)) // output: {}
const fake = Symbol('a')
foobar[fake] = 'fake'
console.log(foobar) // output: { [Symbol(a)]: 'aaa', [Symbol(a)]: 'fake' }
Hope these info will help you.
Related
This is a situation I have ran into a couple of times, it seems like it should be fairly straightforward, but I can't find a solution that doesn't set the type to any
A function takes one of two different objects as the argument, checks which object has been received, and returns the corresponding field.
This is a simplified version of the problem, but the issue is that the two objects are only distinguishable by their properties(which have no overlap), and I can't access any of the properties, because they're not present on the other type.
type Obj1 = {
message: string
}
type Obj2 = {
text: string
}
const getText = (obj: Obj1 |obj2): string => {
if (obj.message) {
return obj.message
}
return obj.text
}
You have to narrow down the type. You can do so by using the in operator.
const getText = (obj: Obj1 | Obj2): string => {
if ("message" in obj) {
return obj.message
}
return obj.text
}
You can cast the object to either Obj1 or Obj2:
type Obj1 = {
message: string
}
type Obj2 = {
text: string
}
const getText = (obj: Obj1 | Obj2): string => {
if ((obj as Obj1).message) {
return (obj as Obj1).message
}
return (obj as Obj2).text
}
The real answer to this problem according to what the question owner asked is this
But there might be a time you are using your defined type with primitive type in this way the above solution is not going to work as the problem I faced
here is the situation
type Obj1 = {
message: string
}
const getText = (obj: Obj1 |string): string => {
if (obj.message) {
return obj.message
}
return obj.text
}
so this scenario the solution stated above would not be perfect for you, so you might need to use typeof ✌️
const getText = (obj: Obj1 | string): string => {
if (typeof obj !== 'string') {
return obj.message
}
return obj.text
}
I recommend typescript-is.
import { is } from 'typescript-is';
...
const getText = (obj: Obj1 | Obj2): string => {
if (is<Obj1>(obj)) {
return obj1.message;
}
return obj2.text;
};
I am trying to achieve a small amount of javascript code that is able to locate a key that contains another key with the most array element occurrences in a string. It's a little hard to explain but I have given an example below. I have tried several filters, finds, and lengthy code loops with no luck. Anything would help, thanks :)
const object = {
keyone: {
tags: ["game","video","tv","playstation"]
},
keytwo: {
tags: ["book", "sport", "camping", "out"]
}
};
const string = "This is an example, out playstaion, tv and video games are cool!";
// I am trying to locate the key that contains the most tags in a string.
// In this case the result I am looking for would be "keytwo",
// because it's tags have greater occurances inside the string (playstaion, tv, video, game/s).
This should do it, though you might want to consider adding keyword stemming.
const object = {
keyone: {
tags: ["game", "video", "tv", "playstation"]
},
keytwo: {
tags: ["book", "sport", "camping", "out"]
}
};
const string = "This is an example, out playstaion, tv and video games are cool!";
result = {}
for (const [key, value] of Object.entries(object)) {
result[key] = value.tags.reduce((acc, item) => (acc += (string.match(item) || []).length), 0)
}
console.log(result)
Result:
{ keyone: 3, keytwo: 1 }
Edit:
How to count:
let result_key;
let result_count = 0;
for (const [key, value] of Object.entries(object)) {
const result = value.tags.reduce((acc, item) => (acc += (string.match(item) || []).length), 0);
if(result > result_count) {
result_count = result;
result_key = key;
}
}
console.log(result_key, result_count)
Result:
keyone 3
I'm coming from mobile app development and do not have much experience with typescript. How one can declare a map object of the form [string:any] ?
The ERROR comes at line: map[key] = value;
Element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'Object'.
No index signature with a parameter of type 'string' was found on type 'Object'.ts(7053)
var docRef = db.collection("accidentDetails").doc(documentId);
docRef.get().then(function(doc: any) {
if (doc.exists) {
console.log("Document data:", doc.data());
var map = new Object();
for (let [key, value] of Object.entries(doc.data())) {
map[key] = value;
// console.log(`${key}: ${value}`);
}
} else {
// doc.data() will be undefined in this case
console.log("No such document!");
} }).catch(function(error: any) {
console.log("Error getting document:", error);
});
You generally don't want to use new Object(). Instead, define map like so:
var map: { [key: string]: any } = {}; // A map of string -> anything you like
If you can, it's better to replace any with something more specific, but this should work to start with.
You need to declare a Record Type
var map: Record<string, any> = {};
https://www.typescriptlang.org/docs/handbook/utility-types.html#recordkeystype
As #Tim Perry mentioned above, use object directly. What I would recommend is to build your own dictionary.
declare global {
type Dictionary<T> = { [key: string]: T };
}
Then you would be able to use
const map: Dictionary<number> = {} // if you want to store number....
Which is easier to read.
I am making a simple note taking app to learn node and ES6. I have 3 modules - App, NotesManager and Note. I am importing the Note class into the NotesManager and am trying to instantiate it in its addNote function. The problem is that even though the import is correct, it turns out to be undefined inside the class definition. A simpler solution would be to just instantiate the NotesManager class and add the Note class to its constructor however, I want to have NotesManager as a static utility class.
Here is my code.
Note.js
class Note {
constructor(title, body) {
this.title = title;
this.body = body;
}
}
module.exports = Note;
NotesManager.js
const note = require("./Note");
console.log("Note: ", note); //shows correctly
class NotesManager {
constructor() {}
static addNote(title, body) {
const note = new note(title, body); //Fails here as note is undefined
NotesManager.notes.push(note);
}
static getNote(title) {
if (title) {
console.log(`Getting Note: ${title}`);
} else {
console.log("Please provide a legit title");
}
}
static removeNote(title) {
if (title) {
console.log(`Removing Note: ${title}`);
} else {
console.log("Please provide a legit title");
}
}
static getAll() {
//console.log("Getting all notes ", NotesManager.notes, note);
}
}
NotesManager.notes = []; //Want notes to be a static variable
module.exports.NotesManager = NotesManager;
App.js
console.log("Starting App");
const fs = require("fs"),
_ = require("lodash"),
yargs = require("yargs"),
{ NotesManager } = require("./NotesManager");
console.log(NotesManager.getAll()); //works
const command = process.argv[2],
argv = yargs.argv;
console.log(argv);
switch (command) {
case "add":
const title = argv.title || "No title given";
const body = argv.body || "";
NotesManager.addNote(title, body); //Fails here
break;
case "list":
NotesManager.getAll();
break;
case "remove":
NotesManager.removeNote(argv.title);
break;
case "read":
NotesManager.getNote(argv.title);
break;
default:
notes.getAll();
break;
}
Is it possible for me to create a strict utility class which I can use without instantiating like in Java? Pretty new here and have tried searching for it without any luck. Thank you for your help.
When you do this:
const note = new note(title, body);
you redefine note shadowing the original note from the outer scope. You need to pick a different variable name.
Something like this should work better:
static addNote(title, body) {
const some_note = new note(title, body); //Fails here as note is undefined
NotesManager.notes.push(some_note);
}
I have a multidimensional object and using Vue, I am trying to make the inner object reactive.
My object looks like this:
data() {
return {
myObject: {}
}
}
And the filled data looks like this:
myObject: {
1: { // (client)
0: "X", // (index) : (value)
1: "Y"
},
2: {
0: "A",
2: "B"
}
}
If I try using:
let value = "X";
let client = 1;
let index = 1;
let obj = {};
obj[client][index] = value;
this.myObject = Object.assign({}, this.myObject, obj);
It throws an error:
TypeError: Cannot set property '0' of undefined
And if I try below, it overwrites the initial values as it is initially setting the object to {}
let obj = {};
obj[index] = value;
let parentObj = {};
parentObj[client] = obj;
this.myObject = Object.assign({}, this.myObject, parentObj);
What is the proper way of adding the values to the multidimensional object?
In javascript, dim2Thing[1][1] = ... expressions require dim2Thing[1] to exist. This is why you get the error you mentioned. So you can do two expressions, which should work fine:
dim2Thing[1] = dim2Thing[1] || {}
dim2Thing[1][1] = otherThing
For the last block, you mention that it "overwrites the initial values"
I think what's actually happening here is just that Object.assign is not recursive. It only merges top-level keys. So if parentObj has a key that over-laps with this.myObj, then sub-keys will be lost.
Object.assign({ a: { b: 2} }, { a: { c: 3 } }) // returns { a: { c: 3 } }
This is what I interpret your code as trying to do - though I am unfamiliar with vue.js at this time, so I cannot assure it will have the desired result to your webpage:
let value = "X";
let client = 1;
let index = 1;
const newObj = Object.assign({}, this.myObject);
// if you have lodash _.set is handy
newObj[client] = newObj[client] || {}; // whatever was there, or a new object
newObj[client][index] = value
this.myObject = newObj
Just use an array, thats reactive by design.
If you need to get elements from the array in your template or anywhere just add a find method
// temp
late
<div v-for="(value, idx) in myArray">{{find(obj => obj.id === idx)}}</div>
methods: {
find (searchFunction) {
return this.myArray.find(searchFunction)
}
}