http://codepen.io/gaearon/pen/xEmzGg?editors=0010 Please explain handleClick() part. Especially prevState.

You really don’t like reading documentation, do you? [image] State and Lifecycle - React A JavaScript library for building user interfaces

handleClick() { this.setState(prevState => ({ isToggleOn: !prevState.isToggleOn })); } setState accepts a function with the first parameter being the current state, the return value of the function will update the state. the initial state is {isToggleOn: true} after a call to handl…

I read docs.But sometimes even I read them I don’t figure out what some part of code does or I am not fully understand. Then I ask for help from more experienced developers to get me more information. If it’s against the rules then please accept my apologies.

I also read the docs but I agree with you SerafirmPoch on this one, how prevState is used to check and set the value of isToggleOn. Please find below my explanation of how prevState is being used to check and change values. I am not a programmer I have made my notes based on observation and assumpt…

This post about React setState method might be helpful. Functional setState is the future of React

Thanks for asking the question. As you said, sometimes we read the documentation but we need a dumystified explanation to understand better :slight_smile:

you give me the priceless explanation to prevState, hats off sir

I have re-read the referenced LifeCycle Methods and the article on Functional setState. I understand that setSet( ) merges whatever object is passed to it and I understand that setSet is evaluating the key of the object passed to determine if the current state has such a key. But none of the explana…

[image] lharley: s that “prevState” is never explicitly defined in the Constructor or anywhere else. How does prevState.isToggleOn become a valid object or value passed to setSet if prevState is not defined? It’s an argument to a function, it represents the state, and isToggleOn is a property…

Thank you for the detailed answer. I appreciate your quick response and taking the time to to to help me understand. Yes, I understand that ‘prevState’ is a parameter or argument for the function and that in the function, I can call the argument anything I choose. But I hope you can understand why …

React(prevState)

Programming

marzelin February 12, 2017, 5:21pm 2

You really don’t like reading documentation, do you?

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React(prevState)

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