How to add multiple classes in Material UI using the classes props?

Question

you can use string interpolation:

<div className={`${this.props.classes.container} ${this.props.classes.spacious}`}>

You could use clsx. I noticed it used in the MUI buttons examples

First install it:

npm install --save clsx

Then import it in your component file:

import clsx from 'clsx';

Then use the imported function in your component:

<div className={ clsx(classes.container, classes.spacious)}>

you can install this package

https://github.com/JedWatson/classnames

and then use it like this

classNames('foo', 'bar'); // => 'foo bar'
classNames('foo', { bar: true }); // => 'foo bar'
classNames({ 'foo-bar': true }); // => 'foo-bar'
classNames({ 'foo-bar': false }); // => ''
classNames({ foo: true }, { bar: true }); // => 'foo bar'
classNames({ foo: true, bar: true }); // => 'foo bar'

// lots of arguments of various types
classNames('foo', { bar: true, duck: false }, 'baz', { quux: true }); // => 'foo bar baz quux'

// other falsy values are just ignored
classNames(null, false, 'bar', undefined, 0, 1, { baz: null }, ''); // => 'bar 1'

To have multiple classes applied to a component, wrap the classes you would like to apply within classNames.

For example, in your situation, your code should look like this,

import classNames from 'classnames';

const styles = theme => ({
  container: {
    display: "flex",
    flexWrap: "wrap"
  },
  spacious: {
    padding: 10
  }
});

<div className={classNames(classes.container, classes.spacious)} />

Make sure that you import classNames!!!

Have a look at material ui documentation where they use multiple classes in one component to create a customized button

You can also use the extend property (the jss-extend plugin is enabled by default):

const styles = theme => ({
  container: {
    display: 'flex',
    flexWrap: 'wrap'
  },
  spaciousContainer: {
    extend: 'container',
    padding: 10
  },
});

// ...
<div className={ this.props.classes.spaciousContainer }>

I think this will solve your problem:

const styles = theme => ({
 container: {
  display: 'flex',
  flexWrap: 'wrap'
},
 spacious: {
  padding: 10
},
});

and in react component:

<div className={`${classes.container} ${classes.spacious}`}>