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Use spread syntax to combine multiple inline style objects in React, for example style={{...style1, ...style2}}. The spread syntax will unpack the key-value pairs of the object into a final object and the styles will be applied to the element.

export default function App() {
  const style1 = {backgroundColor: 'salmon'};
  const style2 = {fontSize: '2rem'};

  return (
    <div>
      <div style={{...style1, ...style2}}>Some content here</div>
    </div>
  );
}

We use spread syntax ...to combine multiple inline style objects in React.

We can merge as many inline style objects as needed.

export default function App() {
  const style1 = {backgroundColor: 'salmon'};
  const style2 = {fontSize: '2rem'};
  const style3 = {color: 'white'};

  return (
    <div>
      <div style={{...style1, ...style2, ...style3}}>Some content here</div>
    </div>
  );
}

We can also add key-value pairs inline after composing the style object.

export default function App() {
  const style1 = {backgroundColor: 'salmon'};
  const style2 = {fontSize: '2rem'};

  return (
    <div>
      <div style={{...style1, ...style2, color: 'white', padding: '2rem'}}>
        Some content here
      </div>
    </div>
  );
}

An easy way to think about spread syntax ...is that we are unpacking the key-value pairs of an object into a new object.

请注意, we styleuse 2 sets of curly braces for the prop. The outer set of curly braces marks the beginning of the expression that will be evaluated.

The inner set of curly braces is an object containing styles and values.

It is important to note that the order in which style objects are combined using the spread syntax is important.

export default function App() {
  const style1 = {backgroundColor: 'salmon'};
  const style2 = {fontSize: '2rem'};
  const style3 = {backgroundColor: 'blue'}; // 👈️ overrides style1

  return (
    <div>
      <div style={{...style1, ...style2, ...style3}}>Some content here</div>
    </div>
  );
}

请注意, objects style1 and style3 set backgroundColorthe property to different values.

If two objects have the same key, the object whose properties are unpacked later wins.

Both objects have a backgroundColor property, but style3's key is unpacked later, so its value overwrites the value of the backgroundColor property in style1.

We may also see examples online Object.assignof using the method to combine inline style objects.

export default function App() {
  const style1 = {backgroundColor: 'salmon'};
  const style2 = {fontSize: '2rem'};

  return (
    <div>
      <div style={Object.assign({}, style1, style2, {color: 'white'})}>
        Some content here
      </div>
    </div>
  );
}

Object.assign()The first argument the method takes is the target object—the object to which the properties of the source object are applied.

The next parameter the method takes is one or more source objects.

The properties of the target object are overwritten by other objects with the same properties in the argument order.

export default function App() {
  const style1 = {backgroundColor: 'salmon'};
  const style2 = {fontSize: '2rem'};

  return (
    <div>
      <div style={Object.assign({}, style1, style2, {backgroundColor: 'lime'})}>
        Some content here
      </div>
    </div>
  );
}

This behavior ...is consistent with the extended syntax.

Either of these two approaches will work, but I’ll stick with the spread syntax ...as I find it easier to read and more commonly used in React.js applications.