Rules
no-direct-mutation-state

no-direct-mutation-state

Rule category

Correctness.

What it does

Disallows direct mutation of this.state.

Why is this bad?

NEVER mutate this.state directly, as calling setState() afterwards may replace the mutation you made. Treat this.state as if it were immutable.

The only place that’s acceptable to assign this.state is in a class component’s constructor.

Examples

Failing

import React from "react";
 
interface ExampleProps {}
 
interface ExampleState {
  ExampleState.foo: stringfoo: string;
}
 
class class ExampleExample extends React.class React.Component<P = {}, S = {}, SS = any>Component<ExampleProps, ExampleState> {
  
Example.state: {
    foo: string;
}
state
= {
foo: stringfoo: "bar", }; Example.render(): React.JSX.Elementrender() { return ( <JSX.IntrinsicElements.div: React.DetailedHTMLProps<React.HTMLAttributes<HTMLDivElement>, HTMLDivElement>div React.DOMAttributes<HTMLDivElement>.onClick?: React.MouseEventHandler<HTMLDivElement> | undefinedonClick={() => { this.
Example.state: {
    foo: string;
}
state
.foo: stringfoo = "baz"
;
// - Do not mutate state directly. Use 'setState()' instead. }} > {this.
Example.state: {
    foo: string;
}
state
.foo: stringfoo}
</JSX.IntrinsicElements.div: React.DetailedHTMLProps<React.HTMLAttributes<HTMLDivElement>, HTMLDivElement>div> ); } }

Passing

import React from "react";
 
interface ExampleProps {}
 
interface ExampleState {
  ExampleState.foo: stringfoo: string;
}
 
class class ExampleExample extends React.class React.Component<P = {}, S = {}, SS = any>Component<ExampleProps, ExampleState> {
  
Example.state: {
    foo: string;
}
state
= {
foo: stringfoo: "bar", }; Example.render(): React.JSX.Elementrender() { return ( <JSX.IntrinsicElements.div: React.DetailedHTMLProps<React.HTMLAttributes<HTMLDivElement>, HTMLDivElement>div React.DOMAttributes<HTMLDivElement>.onClick?: React.MouseEventHandler<HTMLDivElement> | undefinedonClick={() => { this.React.Component<ExampleProps, ExampleState, any>.setState<"foo">(state: ExampleState | ((prevState: Readonly<ExampleState>, props: Readonly<ExampleProps>) => Pick<ExampleState, "foo"> | ExampleState | null) | Pick<...> | null, callback?: (() => void) | undefined): voidsetState({ foo: stringfoo: "baz" }); }} > {this.
Example.state: {
    foo: string;
}
state
.foo: stringfoo}
</JSX.IntrinsicElements.div: React.DetailedHTMLProps<React.HTMLAttributes<HTMLDivElement>, HTMLDivElement>div> ); } }