How to update react state without re-rendering component?

Question

I am building a gallery app where I need to create multiple HTTP requests to pull gallery entries(images & videos).

As gallery will be auto scrolling entries, I am trying to prevent re-rendering component when I make subsequent HTTP requests and update the state.

Thanks

Answer 1

Here's an example of only re-rendering when a particular condition is fulfilled (e.g. finished fetching).

For example, here we only re-render if the value reaches 3.

import React, { Component } from 'react';
import { render } from 'react-dom';

class App extends React.Component { 
  state = { 
    value: 0, 
  }

  add = () => {
    this.setState({ value: this.state.value + 1});
  } 

  shouldComponentUpdate(nextProps, nextState) { 
    if (nextState.value !== 3) { 
      return false;
    }
    return true;
  }

  render() { 
    return (
      <React.Fragment>
        <p>Value is: {this.state.value}</p>
        <button onClick={this.add}>add</button>
      </React.Fragment>
    )
  }
}

render(<App />, document.getElementById('root'));

Live example here.

Answer 2

All data types

useState returns a pair - an array with two elements. The first element is the current value and the second is a function that allows us to update it. If we update the current value, then no rendering is called. If we use a function, then the rendering is called.

const stateVariable = React.useState("value");

stateVariable[0]="newValue"; //update without rendering
stateVariable[1]("newValue");//update with rendering

Object

If a state variable is declared as an object, then we can change its first element. In this case, rendering is not called.

const [myVariable, setMyVariable] = React.useState({ key1: "value" });

myVariable.key1 = "newValue"; //update without rendering
setMyVariable({ key1:"newValue"}); //update with rendering

Array

If a state variable is declared as an array, then we can change its first element. In this case, rendering is not called.

const [myVariable, setMyVariable] = React.useState(["value"]);

myVariable[0] = "newValue"; //update without rendering
setMyVariable(["newValue"]); //update with rendering