322 questions
0
votes
1
answer
125
views
Undetectable JavaScript Error Object Override: Bypassing Standard Detection Mechanisms
I'm attempting to create an undetectable method of overriding the Error object in JavaScript without triggering standard detection mechanisms. My goal is to modify the Error prototype or constructor ...
- 307
3
votes
1
answer
95
views
Is it allowed in javascript to modify the handler after proxy has already been created?
I modify the handler object after proxy's creation, and obtain intended result. But nowhere in mdn document such pattern, can i rely on this pattern to work consistently across browser/in future?
...
- 89
1
vote
1
answer
101
views
When the JavaScript Reflect.get method has a receiver parameter, it returns undefined. How can this situation be reproduced at the language level?
enter image description here
const globalProxy = new Proxy(win.window, {
get(target, p, receiver){
// return undefined
return Reflect.get(target, p, receiver);
// there is a value
// ...
- 11
1
vote
0
answers
74
views
Binding scalar data to HTML element - JavaScript Proxies
I may be guilty of a bit of an XY question here, but I'm doing this out of theoretical interest rather than any immediate need.
My goal is, ultimately, to build a lightweight framework that allows me ...
- 20.2k
0
votes
0
answers
96
views
How to intercept/trap non-existing properties AND methods using JS Proxy?
I need to wrap an immutable object coming from 3rd party code to (a) override some methods and (b) to catch non-existing properties/methods because the object throws an error if a property/method does ...
- 105
-1
votes
1
answer
52
views
Trapping a function call with a proxy does not intercept the arguments
I want to intercept function calls and found that proxies can do that as shown here on MDN using the apply method. However what I quickly found out is that the params passed to the function are not ...
- 123
0
votes
1
answer
80
views
How can I proxy [[set]] on all JavaScript array objects?
I'm trying to proxy the [[set]] method on JavaScript arrays. Is it possible to proxy all arrays, and not just a specific one? My handler would check the object being set in the array and if it ...
- 11
3
votes
1
answer
103
views
Can a Proxy trap assignment to a variable referring to it?
Consider the following Proxy object:
let proxy = new Proxy({}, handler);
If I perform the following assignment, the proxy instance will be overwriten, losing the trap handlers:
proxy = {};
Alright, ...
- 792
2
votes
1
answer
115
views
How to correctly type a JavaScript proxy handler in TypeScript for (Angular Signals-like) reactive state management?
I wanted to create a short documentation and explain the principle of Angular Signals using JavaScript proxies in an example. Then the question came up: could I quickly write it in TypeScript and set ...
- 577
0
votes
1
answer
58
views
Multiple Access to two-dimensional array (using setters/getter via Proxy or Object.defineProperty)
I have a two dimensional array that I need to perform read and write action on from various angles.
Sometimes I need to get/set a single row (easy of course) and sometimes I need to get/set a single ...
-1
votes
1
answer
88
views
Detect direct instances in JavaScript
A couple of years ago, I wanted figure how to create a type check for class A that returns true only for objects instantiated by new A(). For this, I wrote the class like this:
class A {
static #...
- 2,986
0
votes
1
answer
415
views
Why is this object a Proxy only when the page field is 1?
Steps to reproduce:
Open the reproduction
Open the browser console
When the project starts it will errors with:
Uncaught (in promise) DOMException: Failed to execute 'put' on 'IDBObjectStore': #<...
- 4,273
0
votes
1
answer
184
views
JavaScript Proxy not working for opened Window object
I need to Proxy a window object opened with window.open.
So far as I understand it (which is not well), the trivial "handler" here should effectively be the identity operation, passing thru ...
- 50.3k
0
votes
1
answer
53
views
Expression which contains deeply nested proxy object property does not update the same proxy object property
I have a function that takes an object and returns a proxied version of this object, which can be mutated without affecting the original object.
const createProxy4 = (obj) => {
const handler = {
...
- 1,656
0
votes
1
answer
74
views
Mocking an async builder pattern API with proxy
I'm trying to mock knex for testing. Everything seems to work but attaching a proxy to an array as prototype seems to remove the iteratability of arrays.
Here is the mock function. Following works ...
- 23
0
votes
1
answer
186
views
Cannot access puppeteer Proxy in my Jest test (TypeError: Cannot read private member #frameManager from an object whose class did not declare it)
What could be the reason of me not being able to access the Proxy of the CustomPage class in my test file? I get this error...
enter image description here
const puppeteer = require("puppeteer&...
0
votes
1
answer
72
views
Javscript proxy not transparent in Chrome
A common trick sites use to protect against reverse engineering is to prevent Javascript from executing correctly when the developer tools are open. Usually, this relies on an object logged to the ...
- 3,068
0
votes
0
answers
90
views
Trap array changes (add/delete) inside object of proxy
I am trying to track some array changes inside of proxyfied object.
For example:
object = {
count: 0,
input: ``,
tasks: [ ]
}
and I need to track changes of object.tasks.
The problem ...
- 1
0
votes
1
answer
131
views
Debounce "setting" of values in proxy trap without delay/timeout
I try to understand how i can debounce a "set" trap in javascript proxy.
function debounce(func, wait, immediate = false) {
let timeout = null;
return function(...args) {
let ...
- 4,049
1
vote
2
answers
146
views
Can a Proxy detect that a subclass is adding methods to a class?
Given a class like:
class A {}
Is it possible to modify in any way so that I can proxy when methods are subclassed like so:
// proxy the `A` object in some way
const handler = {
get(target, ...
- 390
0
votes
0
answers
74
views
How to attach toString to proxy handler
Consider this code:
handler.toString = function() {
return Reflect.get(original,'toString');
}
handler.apply = scope.exportFunctionWithName(function(target, thisArgs, args){
try {
...
- 556
-3
votes
1
answer
374
views
How can I use proxy with spread operator or object.assign?
I need to have methods and store bound to 'this' in my callback function, but when I use the spread operator it doesn't work.
The reason for this as far as I know is that the spread operator returns a ...
- 473
0
votes
1
answer
324
views
myRef.value is holding a Proxy even tho it should hold a simple array
I am doing a simple app that fetches data (my tasks) from my PocketBase(BaaS like Firebase).
I want to store my tasks into a ref because it could change overtime (ex: user modify the name of it).
I am ...
- 13
0
votes
0
answers
90
views
How to globally track property changes and DOM mutations in JavaScript?
I am working on a project where I need to monitor changes in the DOM, specifically tracking any and all JavaScript property changes that affect the DOM elements. My goal is to listen for any 'set' ...
- 67
1
vote
3
answers
146
views
How to always apply a method before executing another method via a proxy?
I have the following code where I want to invoke the instance method connect before proceeding with the invocation of every other instance method of the TelegramClient class. How can this be achieved ...
- 37
0
votes
0
answers
26
views
Typescript derives different types when a static method is called from inside or outside a class
Can someone help me explain the behavior of typescript in this example. I have no idea what is going on here. Why is childProxy1.foo not resolved while childProxy2.foo is resolved correctly? Why is ...
1
vote
1
answer
102
views
Is there a nicer way to handle isLoading checks in react? [closed]
In React we very often load data which is for some time undefined/null or some placeholder value. Now there are many ways to use loading skeletons, but in my project we have the skeletons rather low ...
- 1,198
0
votes
1
answer
81
views
A proxied JS child class assigns a wrong prototype to an instance
Some interesting case which I don't understand.
I proxy classes and extend a child class from a proxied base class.
When a child is constructed inside the construct trap for some reason a wrong ...
- 26.1k
2
votes
2
answers
1k
views
ES6 Proxy to return an iterable array
I need to exercise some code in data mapping functions. For this, I need a proxy that returns an iterable array with one element (itself; an iterable array) when any property is requested. This will ...
- 4,930
0
votes
2
answers
71
views
JavaScript proxies : aggregate notifications after array sort
I would like to find a way to get only one notification after an array sort
Is there a way? Thank you
const callback = function () {
console.log (...arguments)
}
const array = [2,1]
const handler = {...
- 619
0
votes
1
answer
62
views
Why is Proxy being called for nested elements?
I'm attempting to abstract some Cypress methods into a helper object using getters.
The intended behavior is that I can do something like this:
todoApp.todoPage.todoApp.main.rows.row
.first()....
- 1,537
1
vote
3
answers
159
views
How can I detect changes to arbitrary private members with an ES6 proxy in Javascript?
I am working on building a 2D renderer with the Javascript canvas API, and I am trying to improve performance by skipping renders when no changes to the state of any renderable objects have occurred.
...
- 15
0
votes
1
answer
1k
views
Typescript: function should return proxy object of generic object type
The following function should create a proxy object with a specific handler, but typescript is throwing a type error when I try it that way.
function createProxiedObject<T extends object>(obj: T)...
- 571
2
votes
1
answer
4k
views
Proxy object in Vue 3 will not let me access data
I have an app in Vue 3 where I make a call to the back end of my code to get data. The data is returned nested in JSON arrays and objects, and I then assign the data to a property in my component. I ...
- 2,608
-1
votes
1
answer
493
views
Javascript construct trap not working in class returning proxy
I am trying to create a little javascript two way form binder using proxies. I am stuck on how I can intercept 'new' calls. I use a 'construct' trap but it doesn't fire. Here is my code, I have ...
- 465
-2
votes
2
answers
535
views
How to proxy Function.prototype?
I tried to proxy Function.prototype.
I created a new Proxy and rewrote the toString method, however console.log('cas') doesn't work, why?
Function.prototype = new Proxy(Function.prototype, {
get: ...
- 121
1
vote
1
answer
71
views
For an instance field which is an array value, how does one handle additional tasks whenever the array mutates by e.g. pushing into or splicing it?
The set accessor does not take place whenever one does mutate the Crumbs class property value by e.g pushing into it.
I'm trying to create a class property via set syntax which I expect to handle an ...
- 502
1
vote
1
answer
469
views
why are target and receiver not the same in this javascript proxy?
I am working with JavaScript Proxy and do not understand why the target and the receiver are different in both the get() and set() traps. They appear to be the same (based on console logging). The ...
- 5,348
1
vote
1
answer
308
views
Implement a dynamic lazy proxy collection class on typescript
I'm trying to implement a lazy database connection collection in typescript. I'm creating a class called DatabaseCollection and my idea is to use a proxy to lazy load the connections (I'm using knex ...
- 19.9k
0
votes
1
answer
176
views
Value of this inside a Proxy trap
I have the following code:
function delay(f, ms) {
return new Proxy(f, {
apply(target, thisArg, args) {
console.log(this)
console.log(thisArg)
...
1
vote
0
answers
375
views
JavaScript Error: caught (in promise) TypeError: 'set' on proxy: trap returned falsish for property
I'm attempting to add an "eventlistener" of sorts to trigger when all of the application resources have completed loading. If I understand Proxies correctly, "this is the way" to ...
- 905
1
vote
1
answer
586
views
Is it possible to get parent property name of nested object in set method of Proxy object?
https://stackoverflow.com/a/41300128
↑ completely based on this code
var validator = {
get(target, key) {
if (typeof target[key] === 'object' && target[key] !== null) {
return new ...
- 412
0
votes
1
answer
38
views
How do I roll back the values of the items or collections after an unexpected error?
<q-select v-model="item" :options="colect">
<q-input v-model="item.name">
const colect = ref([... ])
const item = ref({... })
The dilemma is that, when ...
0
votes
1
answer
60
views
Why object is not proxied like an argument in function
i have an interesting example of code that's not working like i'm expected.
I really dont understand why my obj wouldnt proxy.
I'm expect that obj ill proxy via link, but it's not. Can anyone explain ...
- 83
1
vote
1
answer
1k
views
TypeScript types for Proxy with dynamic properties
I want to type a JavaScript Proxy that allows access to arbitrary properties. A contrived example, an object that maps every property to it's own property name:
const proxy = new Proxy({}, {
get(...
- 2,858
6
votes
3
answers
12k
views
'get' on proxy: property 'items' is a read-only and non-configurable data property on the proxy target but the proxy did not return its actual value
What does this JavaScript error actually mean? I'm not asking about my specific case, just generally how is this error message meant to be understood?
TypeError: 'get' on proxy: property 'items' is a ...
- 2,122
0
votes
0
answers
18
views
React - Use JavaScript Proxy Object to update with Custom Hook [duplicate]
I am seeing a weird behavior with a simple custom React Hook I am trying to come up with. Any ideas on why it's not working as intended would be greatly appreciated.
So I have a custom hook called ...
1
vote
0
answers
32
views
argument is `undefined` in reflection function call [duplicate]
I have the following functional logic code:
const trans = {}
trans['toCssClass'] = (someListing) => {
// <-- someListing here is undefined
console.log(someListing)
someListing.a = ...
- 53
0
votes
0
answers
111
views
How can I make my library compatible with libraries that use Proxies
I've written a library that relies on equality checks. Example:
export class Item {
constructor(opts) {
if (typeof opts.name !== 'string') throw new TypeError('Name should be a string');
if (...
- 393
0
votes
0
answers
229
views
How to Proxy Built-In JS Object?
I want to proxy some built in object primitives in JS, for example, “Number” or “String” object wrappers. However it seems the Proxy object ends up reporting as a normal JS object when passed to some ...
- 512