ReactJS | Introduce Events in Expense Manager App

Hello folks! welcome back to a new section of our tutorial on ReactJS. In this section of our tutorial on ReactJS, we will be studying about how to introduce Events in Expense Manager App.

Let us perform some event management in our React expense application. We can try to highlight the expense entry item in the table when the user moves the cursor over it.

Open expense-manager application in your favorite editor.

Next, open ExpenseEntryItemList.js file and then include a method handleMouseEnter to handle the event fired when the user moves the mouse pointer into the expense items.

handleMouseEnter(e) { 
   e.target.parentNode.classList.add("highlight"); 
}

Here,

• Event Handler tries to find the parent node (tr) of the event target (td) node via parentNode method. parentNode method is the standard DOM method used to find the immediate parent of the current node.

• As soon as the parent node is found, event handler accesses the list of the CSS class attached to the parent node and then adds highlight class using add method classList is the standard DOM property to get list of class attached to the node and we can use it to add/remove class from a DOM node.

Next, add a method handleMouseLeave to handle the event fired when the user moves out of the expense item.

handleMouseLeave(e) { 
   e.target.parentNode.classList.remove("highlight"); 
}

READ: ReactJS | Create an Event-Aware Component

Here, Event handler removes the "highlight" class from the DOM.

Next, include a method handleMouseOver in order to check where the mouse is currently positioned. It is optional to find the position of the mouse pointer in the DOM.

handleMouseOver(e) { 
   console.log("The mouse is at (" + e.clientX + ", " + e.clientY + ")"); 
}

Bind all event handlers in the constructor of the component.

this.handleMouseEnter = this.handleMouseEnter.bind(); 
this.handleMouseLeave = this.handleMouseLeave.bind(); 
this.handleMouseOver = this.handleMouseOver.bind();

Next, attach all of the event handlers to the corresponding tag in the render method.

render() {
   const lists = this.props.items.map((item) =>
      <tr key={item.id} onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
         <td>{item.name}</td>
         <td>{item.amount}</td>
         <td>{new Date(item.spendDate).toDateString()}</td>
         <td>{item.category}</td>
      </tr>
   );
   return (
      <table onMouseOver={this.handleMouseOver}>
         <thead>
            <tr>
               <th>Item</th>
               <th>Amount</th>
               <th>Date</th>
               <th>Category</th>
            </tr>
         </thead>
         <tbody>
            {lists}
         </tbody>
      </table>
   );
}

The final and complete source code of the ExpenseEntryItemList is as follows -

import React from 'react';
import './ExpenseEntryItemList.css';

class ExpenseEntryItemList extends React.Component {
   constructor(props) {
      super(props);

      this.handleMouseEnter = this.handleMouseEnter.bind();
      this.handleMouseLeave = this.handleMouseLeave.bind();
      this.handleMouseOver = this.handleMouseOver.bind();
   }
   handleMouseEnter(e) {
      e.target.parentNode.classList.add("highlight");
   }
   handleMouseLeave(e) {
      e.target.parentNode.classList.remove("highlight");
   }
   handleMouseOver(e) {
      console.log("The mouse is at (" + e.clientX + ", " + e.clientY + ")");
   }
   render() {
      const lists = this.props.items.map((item) =>
         <tr key={item.id} onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
            <td>{item.name}</td>
            <td>{item.amount}</td>
            <td>{new Date(item.spendDate).toDateString()}</td>
            <td>{item.category}</td>
         </tr>
      );
      return (
         <table onMouseOver={this.handleMouseOver}>
            <thead>
               <tr>
                  <th>Item</th>
                  <th>Amount</th>
                  <th>Date</th>
                  <th>Category</th>
               </tr>
            </thead>
            <tbody>
               {lists}
            </tbody>
         </table>
      );
   }
}
export default ExpenseEntryItemList;

READ: ReactJS | Component Collection

Open the css file, ExpenseEntryItemList.css and add a css class, highlight.

tr.highlight td { 
   background-color: #a6a8bd; 
}

Next, open the index.js file and make use of the ExpenseEntryItemList component.

import React from 'react';
import ReactDOM from 'react-dom';
import ExpenseEntryItemList from './components/ExpenseEntryItemList'

const items = [
   { id: 1, name: "Pizza", amount: 80, spendDate: "2020-10-10", category: "Food" },
   { id: 2, name: "Grape Juice", amount: 30, spendDate: "2020-10-12", category: "Food" },
   { id: 3, name: "Cinema", amount: 210, spendDate: "2020-10-16", category: "Entertainment" },
   { id: 4, name: "Java Programming book", amount: 242, spendDate: "2020-10-15", category: "Academic" },
   { id: 5, name: "Mango Juice", amount: 35, spendDate: "2020-10-16", category: "Food" },
   { id: 6, name: "Dress", amount: 2000, spendDate: "2020-10-25", category: "Cloth" },
   { id: 7, name: "Tour", amount: 2555, spendDate: "2020-10-29", category: "Entertainment" },
   { id: 8, name: "Meals", amount: 300, spendDate: "2020-10-30", category: "Food" },
   { id: 9, name: "Mobile", amount: 3500, spendDate: "2020-11-02", category: "Gadgets" },
   { id: 10, name: "Exam Fees", amount: 1245, spendDate: "2020-11-04", category: "Academic" }
]
ReactDOM.render(
   <React.StrictMode>
      <ExpenseEntryItemList items={items} />
   </React.StrictMode>,
   document.getElementById('root')
);

Next, serve the application making use of npm command.

npm start

Next, open the web browser and then enter http://localhost:3000 in the address bar and press enter.

The application will respond to the mouse events and highlight the currently selected row.

Item	Amount	Date	Category
Pizza	80	Sat Oct 10 2020	Food
Grape Juice	30	Man Oct 12 2020	Food
Cinema	210	Fri Oct 16 2020	Entertainment
Java Programming book	242	Thu Oct 15 2020	Academic
Mango Juice	35	Fri Oct 16 2020	Food
Dress	2000	Sun Oct 25 2020	Cloth
Tour	2555	Thu Oct 29 2020	Entertainment
Meals	300	Fri Oct 30 2020	Food
Mobile	3500	Mon Nov 02 2020	Gadgets
Exam Fees	1245	Wed Nov 04 2020	Academic

READ: ReactJS | Nested Components

Alright guys! This is where we are going to be rounding up for this tutorial. In our next tutorial, we will be studying about ReactJS State Management.

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Thanks for reading and bye for now.