javascript - Too much recursion when updating state in react - Stack Overflow

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In this example, when I try to update the state during the ponentDidUpdate life cycle callback, I get a too much recursion error. How should I be updating the state?

import React from 'react';

class NotesContainer extends React.Component {
  constructor(props) {
    super(props);
    this.state = { listOfShoppingItems: [] };
  }

  ponentDidUpdate(nextProps, nextState) {
    let newShoppingItems = this.calculateShoppingItems();
    this.setState({ listOfShoppingItems: newShoppingItems });
  }

  calculateShoppingItems() {
    let shoppingItemsCart = []

    if (this.props.milk < 3) {
      let value = "Buy some milk";
      shoppingItemsCart.push(value);
    }

    if (this.props.bread < 2) {
      let value = "Buy some bread";
      shoppingItemsCart.push(value);
    }

    if (this.props.fruit < 10) {
      let value = "Buy some fruit";
      shoppingItemsCart.push(value);
    }

    if (this.props.juice < 2) {
      let value = "Buy some juice";
      shoppingItemsCart.push(value);
    }

    if (this.props.sweets < 5) {
      let value = "Buy some sweets";
      shoppingItemsCart.push(value);
    }

    return shoppingItemsCart;
  }

  render() {
    return (
      <div>
        Etc...
      </div>
    );
  }
}

export default NotesContainer;

In this example, when I try to update the state during the ponentDidUpdate life cycle callback, I get a too much recursion error. How should I be updating the state?

import React from 'react';

class NotesContainer extends React.Component {
  constructor(props) {
    super(props);
    this.state = { listOfShoppingItems: [] };
  }

  ponentDidUpdate(nextProps, nextState) {
    let newShoppingItems = this.calculateShoppingItems();
    this.setState({ listOfShoppingItems: newShoppingItems });
  }

  calculateShoppingItems() {
    let shoppingItemsCart = []

    if (this.props.milk < 3) {
      let value = "Buy some milk";
      shoppingItemsCart.push(value);
    }

    if (this.props.bread < 2) {
      let value = "Buy some bread";
      shoppingItemsCart.push(value);
    }

    if (this.props.fruit < 10) {
      let value = "Buy some fruit";
      shoppingItemsCart.push(value);
    }

    if (this.props.juice < 2) {
      let value = "Buy some juice";
      shoppingItemsCart.push(value);
    }

    if (this.props.sweets < 5) {
      let value = "Buy some sweets";
      shoppingItemsCart.push(value);
    }

    return shoppingItemsCart;
  }

  render() {
    return (
      <div>
        Etc...
      </div>
    );
  }
}

export default NotesContainer;

• javascript
• reactjs

Share Improve this question Follow edited Aug 16, 2017 at 15:45 Mike Walton 4,38633 gold badges4444 silver badges5454 bronze badges asked Aug 25, 2015 at 7:55 SimpletonSimpleton 6,4151212 gold badges5555 silver badges8989 bronze badges

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1 Answer 1

Sorted by: Reset to default 9

ponentDidUpdate is triggered when either the props or the state has changed. If you change the state in this method, you are causing an infinite loop (unless you implement shouldComponentUpdate).

It looks like your state changes when you receive new props, therefore ponentWillReceiveProps seems a good place. From the docs:

Invoked when a ponent is receiving new props. This method is not called for the initial render.

Use this as an opportunity to react to a prop transition before render() is called by updating the state using this.setState(). The old props can be accessed via this.props. Calling this.setState() within this function will not trigger an additional render.

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