我觉得问这个问题可能很傻,但相信我,我是个新手.谁能给我解释一下为什么我们在ReactjS中使用prevState.我努力go 理解,但失败了.
Here is my code. Please Help me to understand
state = {
placeName : '',
places : []
}
placeSubmitHanlder = () => {
if(this.state.placeName.trim()===''){
return;
}
this.setState(prevState => {
return {
places : prevState.places.concat(prevState.placeName)
};
});
};