如何避免改变this.state或redux对象

Question

For example, if I want to do any operation on this.state or some other object, such as Object.keys(this.state).map() to get access to all the values in the object.

Is it bad practice to do this?

Object.keys(this.state).map(k => this.state[k]);

Thanks

Answer 1

In React, you should only mutate this.state using this.setState() so that React knows when to re-render components.

The line of code you've written is fine, because you're not actually modifying the state object. You've already created a new array using Object.keys .

If however, you want to copy this.state without modifying it, try the following.

const state = {...this.state};

// Or 

const state = Object.assign({}, this.state);

Answer 2

React Mutating State.

let state = {
    age    : 25,
    name   : 'Robin',
    friends: ['Barney', 'Ted']
}

Change Age

this.setState({age: 26}) 

Change Name

this.setState({name: 'Lily'}) 

Add Friend

this.setState({ 
    friends: this.state.friends.concat(['Marshall'])
})

Try this library immutability-helper for complex state updates.