1. Type null undefined Boolean that cannot be displayed in {}
State ={flag:true} {this.state.flag?” Nihao “:null} or {flag && ‘nihao’}
(2) How to render: to string
this.state={ test1 = null, test2 = undefined, test3 = true }
2. Objects cannot be subclasses of JSX
person:{ name:”sdf”, age:65, }
Direct error
3. Embed expressions
function
5. Conditional judgment
6. Filter traversal
To simplify the
7. Capture
8. Type verification
Class component adds propTypes
9. The father the son
10. Slot
11. Multiple components pass values using… Props to pass
12.context
Functional component
nested
13. SetState is designed to be asynchronous
Catch changes in time
14 Merge and accumulate
15 Controlled components <select name=”fruits” value={this.state.fruits} onChange={e= > this.handlechange (e)}> value Sets the default value
When multiple form elements process input data, use “name” to extract common code
16 Advanced component login detection
17 protals
Use Fragment when DIV does not need to be wrapped around it
Or you can use phrasing, but phrasing cannot add any attributes
To optimize performance, add key to list, but phrase method cannot add attribute, error
19 Use the template string to call the function
For styled-compoents, active in span should be used &
Use variables to change styles dynamically
1.
2. Note: Labels must be components. Figure 3 does not work
invalid
Shared data
21 Dynamically add classes
Use classnames import classnames from ‘classnames’
If this.state.titile is converted to a Boolean value of false, it is not displayed
