React Js for Web Development > Components

Understanding Index.js

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The indexOf() method returns the position of a value in a string's first occurrence. If the value cannot be retrieved, the indexOf() method returns -1.

Reordering an item alters the index if the key is an index. As a result, the component state may become jumbled, and the old key may be used for a different component instance. React can't tell if an element was removed or merely the content was updated without a unique key.

indexOf returns the first index in the array where a specified element can be found, or -1 if it does not exist. So index is simply the counter's index in counters. You're making a comparison between an object (counter) and a number ( index ).

  • The indexOf() method is used for a single-dimensional array of primitive datatypes such as string, number, and so on.
  • When looking for an index value from an object element, the findIndex() method is used.

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Very helpful course in learning ReactJS

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VERY GOOD COURSE OF REACT JS

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I gave it 5 stars for their work. Topics are covered very well.but one thing which I would like to say to the teachers that you covered very good but try to cover more things and use less English words. Except this all things are best.

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Amazing content.

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This series is usefull for just starting and building confident. Go further and explore more about React JS

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Course Content

  1. About Course
    4m 35s
  2. What is React
    4m 5s
  3. Single Page Application
    3m 12s
  4. Why Choose React for Web Development?
    6m 30s
  5. Real Time Example
    3m 46s
  6. React VS Angular VS vue
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  7. Setting up the first project
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  1. Components in React
    10m 37s
  2. How to Create Components in React
    7m 14s
  3. Installation of Node
    7m 57s
  4. Creating the First Project
    8m 41s
  5. Understanding File Structure
    10m 3s
  6. Understanding Index.js
    9m 38s
  7. Introduction to JSX
    8m 32s
  8. Custom Components
    9m 5s
  9. Assignmnet : Introduction
    3m 48s
  10. Assignment : Components
    3m 47s

  1. Adding Template in JSX React
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  2. Adding Styles in JSX React
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  3. Dynamic Data in JSX React
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  4. Data Passing in React
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  5. Accessing Props in React
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  6. Implementing JS Code in JSX React
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  7. Creating Single Responsibility Components in React
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  8. Children Props in React
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  9. Other Details in JSX React
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  10. Assignment : JSX
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  1. Event Listening in React
    8m 16s
  2. Event Handling in React
    11m 13s
  3. States in React
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  4. Adding Forms in React
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  5. Feching Form Inputs in React
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  6. Storing Form Inputs in React
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  7. Another Method for Storing Form Inputs in React
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  8. Submitting Forms in React
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  10. Component Communication in React
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  11. Adding Custom Components in React
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  14. Updating States in React
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  1. Iterating the List in JSX React
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  14. Assignment : Iterations and conditions
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  3. Dynamic Classes
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  4. CSS Scope in React
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  5. Styled Components in React
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  6. Responsive Styling in React
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  7. Style Module in React
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  8. Adding Media Queries in React
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  9. Assignment : Styling
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  1. Handling Syntax Errors in React
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  2. Debugging in React
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  3. Developer Tools in React
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  4. Assignment : Error and Debugging
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  1. Creating Application in React
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  2. Container Component
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  3. Adding Styles to Inputs
    7m 13s
  4. Reusable Component
    11m 9s
  5. Managing Data in React
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  6. Resetting & Validating Form Data in React
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  7. Adding Data to List in React
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  8. Adding State to List in React
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  9. Adding Modal in React
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  10. Error Boundaries in React
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  11. Assignment : Dialogs and Modals
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  7. Assignment : Fragments and portals
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  2. Effect Hooks in React Part-2
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  14. Adding Context in React
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  20. limitations of React Context
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  18. Validity in React Forms
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    8m 4s
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    10m 50s
  23. Using Reducer in React
    13m 45s
  24. Assignment : Custom Hooks and Forms
    3m 50s

  1. Introduction to Redux
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  2. Redux vs Context API
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  6. Installing Redux with React
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  7. Firebase Authentication for Login Page
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    4m 39s
  10. Handling Protected Resources
    9m 29s
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    9m 23s
  12. Improvising User Experience
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  13. Logout in React
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  1. Course Summary
    4m 47s

  1. Interview Questions in React js
    29m 13s

  1. Career Guideline
    2m 40s
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