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June 15, 2016 19:20
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Example where React.setState causes issues
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class Select extends React.Component { | |
constructor(props, context) { | |
super(props, context) | |
this.state = { | |
selection: props.values[0] | |
}; | |
} | |
render() { | |
return ( | |
<ul onKeyDown={this.onKeyDown} tabIndex={0}> | |
{this.props.values.map(value => | |
<li | |
className={value === this.state.selection ? 'selected' : ''} | |
key={value} | |
onClick={() => this.onSelect(value)} | |
> | |
{value} | |
</li> | |
)} | |
</ul> | |
) | |
} | |
onSelect(value) { | |
this.setState({ | |
selection: value | |
}) | |
this.fireOnSelect() | |
} | |
onKeyDown = (e) => { | |
const {values} = this.props | |
const idx = values.indexOf(this.state.selection) | |
if (e.keyCode === 38 && idx > 0) { /* up */ | |
this.setState({ | |
selection: values[idx - 1] | |
}) | |
} else if (e.keyCode === 40 && idx < values.length -1) { /* down */ | |
this.setState({ | |
selection: values[idx + 1] | |
}) | |
} | |
this.fireOnSelect() | |
} | |
fireOnSelect() { | |
if (typeof this.props.onSelect === "function") | |
this.props.onSelect(this.state.selection) /* not what you expected..*/ | |
} | |
} | |
ReactDOM.render( | |
<Select | |
values={["State.", "Should.", "Be.", "Synchronous."]} | |
onSelect={value => console.log(value)} | |
/>, | |
document.getElementById("app") | |
) |
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