Unable to assign the value 'hello' to an undefined property in TypeScript

Question

Unable to assign the value 'hello' to an undefined property in TypeScript

I'm attempting to define a class in TypeScript, but I keep encountering the error shown below.

Here is the execution log where the error occurs:

[LOG]: "adding" 
[LOG]: undefined 
[ERR]: Cannot set property 'hello' of undefined

class CustomDataStructure {
    private _data: any;

    public CustomDataStructure() {
        this._data = {};
    }

    public addItem(value: string) {
        console.log("adding");
        console.log(this._data)
        this._data[value] = new Date().getTime();
    }

    public removeItem(key: string) {
        delete this._data[key];
    }

    public showData() {
        return this._data;
    }
}


let ss = new CustomDataStructure();
ss.addItem("hello");

javascript typescript

Answer 1

Answer №1

In order to initialize this._data with an empty object, you must invoke a constructor that accomplishes this:

class DataHandler {
 private _data: any;

 constructor() {
     this._data = {};
 }

 public addEntry(value: string) {
    console.log("Adding new entry");
    console.log(this._data)
    this._data[value] = new Date().getTime();
    console.log(this._data)
 }

 public removeEntry(key: string) {
    delete this._data[key];
 }

 public displayData() {
    return this._data;
 }
}


let dh = new DataHandler();
dh.addEntry("world");

Answer 2

In order to initialize this._data with an empty object, you must invoke a constructor that accomplishes this:

class DataHandler {
 private _data: any;

 constructor() {
     this._data = {};
 }

 public addEntry(value: string) {
    console.log("Adding new entry");
    console.log(this._data)
    this._data[value] = new Date().getTime();
    console.log(this._data)
 }

 public removeEntry(key: string) {
    delete this._data[key];
 }

 public displayData() {
    return this._data;
 }
}


let dh = new DataHandler();
dh.addEntry("world");

Answer 3

Answer №2

class CustomDataStructure {
    private _data: any;

    constructor() {
        this._data = {};
    }

    public addItem(value: string) {
        console.log("adding");
        console.log(this._data)
        this._data[value] = new Date().getTime();
    }

    public removeItem(key: string) {
        delete this._data[key];
    }

    public displayData() {
        return this._data;
    }
}
let newDataStruct = new CustomDataStructure();
newDataStruct.addItem("Hello World")
console.log(newDataStruct.displayData())

Answer 4

class CustomDataStructure {
    private _data: any;

    constructor() {
        this._data = {};
    }

    public addItem(value: string) {
        console.log("adding");
        console.log(this._data)
        this._data[value] = new Date().getTime();
    }

    public removeItem(key: string) {
        delete this._data[key];
    }

    public displayData() {
        return this._data;
    }
}
let newDataStruct = new CustomDataStructure();
newDataStruct.addItem("Hello World")
console.log(newDataStruct.displayData())

Unable to assign the value 'hello' to an undefined property in TypeScript

Answer №1

Answer №2

Similar questions

Having difficulty toggling checkboxes within a grid using the select all feature

Ways to rearrange an object with javascript

JavaScript Date displaying the string in the format YYYY/MM/DD HH:MM

Exploring the world of Typescript and Angular Filter functionalities

Is the IE7 Modal Dialog Misaligned?

Using HttpClient to display data on the DOM

"When attempting to render a Node inside the render() method in React, the error message 'Objects are not valid as a React child' is

Using Javascript and Node.js, a child class instance in ES5 can access a method belonging to its parent

How do I define the specific icon to display on the splash screen for progressive web apps?

The JQuery function fails to execute following a successful Ajax request

Attaching Picture From Array To Vue

How to access class type arguments within a static method in Typescript: A clever solution

Dealing with a Jquery/Javascript Dilemma

Issue encountered with ng-include compatibility in Angular 5

`Three.js and its efficient use of JavaScript for enhancing performance``

Tips on avoiding redirection when submitting a form

Dynamically fetching and uploading files from a specific path using Node.js, Express, and Angular 1.x

Triggering the AJAX function in the main window

node js retrieves information from the request body

What steps do I need to take to retrieve my paginated data from FaunaDB in a React frontend application?