样式组件内的 if 语句

Question

export enum SizeEnum {
    Small,
    Large
}

export interface ICheckbox {
    Size: SizeEnum;
}

const Box = styled.div`
    height: 20px;
    width: 20px;
`

In the above code I want to be able to conditionally change the height and width value of <Box> based on the prop. How do I do this?

Answer 1

See Logical Operators and Adapting based on props for more info.

// Box.
const Box = styled.div`

  height: ${({Size}) => 
    Size === 'Small' && '25px' ||
    Size === 'Large' && '100px' || 
    '50px'
  };

  width: ${({Size}) => 
    Size === 'Small' && '25px' || 
    Size === 'Large' && '100px' || 
    '50px'
  };

`

// Render.
<Box/> // 50px - Normal.
<Box Size="Small"/> // 25px - Small.
<Box Size="Large"/> // 100px - Large.

Answer 2

Another way to do this, if you want to add several css styles.

const Box = styled.div`
    height:100px;
    width:100px;
    ${props => props.Size === 'Small' && css`
         height:20px;
         width:20px;
    `}
`

Answer 3

You can use the ternary operator

const Box = styled.div`
height: ${props => props.Size === 'Small' ? '20px' : '40px'}
width: ${props => props.Size === 'Small' ? '20px' : '40px'}
`

Reference: https://www.styled-components.com/docs/basics

Answer 4

You can use the elvis operator in something like this:

${(props) => props.someValue ? css` width: 20px;` : css` width: 100px; `}

Hope this helps someone looking into how to use logical operators in React styled components .

Answer 5

We can add the if-checks just like jsx

const Box = styled.div`
    height:100px;
    width:100px;
    ${props => props.Size === 'Small' && `
         height:20px;
         width:20px;
    `}
` 

Note: No need to include the word css