problem description
in html, you use a property that state does not define, but if you use the componentWillMount () method to define this property, the result will be an error. The browser prompts that the property is not defined and cannot refer to
Cannot read property"0" of undefined
the environmental background of the problems and what methods you have tried
you can only define it
.related codes
/ / Please paste the code text below (do not replace the code with pictures)
this.state = {
// menu:[{name:""}]
}
what result do you expect? What is the error message actually seen?
speechless, didn"t you say that render is behind componentWillMount