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Traversing the DOM

Traversing a document with Cheerio allows you to select and manipulate specific elements within the document. Whether you want to move up and down the DOM tree, move sideways within the tree, or filter elements based on certain criteria, Cheerio provides a range of methods to help you do so.

In this guide, we will go through the various methods available in Cheerio for traversing and filtering elements. We will cover methods for moving down the DOM tree, moving up the DOM tree, moving sideways within the tree, and filtering elements. By the end of this guide, you will have a good understanding of how to use these methods to select and manipulate elements within a document using Cheerio.

提示

This guide is intended to give you an overview of the various methods available in Cheerio for traversing and filtering elements. For a more detailed reference of these methods, see the API documentation.

Moving Down the DOM Tree​

Cheerio provides several methods for moving down the DOM tree and selecting elements that are children or descendants of the current selection.

find​

The find method allows you to locate specific elements within a selection. It takes a CSS selector as an argument and returns a new selection containing all elements that match the selector within the current selection.

Here's an example of using find to select all <li> elements within a <ul> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>Item 1</li>
    <li>Item 2</li>
  </ul>`,
);

const listItems = $('ul').find('li');
render(<>List item count: {listItems.length}</>);
结果
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children​

The children method allows you to select the direct children of an element. It returns a new selection containing all direct children of the current selection.

Here's an example of using children to select all <li> elements within a <ul> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>Item 1</li>
    <li>Item 2</li>
  </ul>`,
);

const listItems = $('ul').children('li');
render(<>List item count: {listItems.length}</>);
结果
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contents​

The contents method allows you to select all children of an element, including text and comment nodes. It returns a new selection containing all children of the current selection.

Here's an example of using contents to select all children of a <div> element:

实时编辑器
const $ = cheerio.load(
  `<div>
    Text <p>Paragraph</p>
  </div>`,
);

const contents = $('div').contents();
render(<>Contents count: {contents.length}</>);
结果
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Moving Up the DOM Tree​

Cheerio provides several methods for moving up the DOM tree and selecting elements that are ancestors of the current selection.

parent​

The parent method allows you to select the parent element of a selection. It returns a new selection containing the parent element of each element in the current selection.

Here's an example of using parent to select the parent <ul> element of a <li> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>Item 1</li>
  </ul>`,
);

const list = $('li').parent();
render(<>{list.prop('tagName')}</>);
结果
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parents and parentsUntil​

The parents method allows you to select all ancestor elements of a selection, up to the root element. It returns a new selection containing all ancestor elements of the current selection.

The parentsUntil method is similar to parents, but allows you to specify an ancestor element as a stop point. It returns a new selection containing all ancestor elements of the current selection up to (but not including) the specified ancestor.

Here's an example of using parents and parentsUntil to select ancestor elements of a <li> element:

实时编辑器
const $ = cheerio.load(
  `<div>
    <ul>
      <li>Item 1</li>
    </ul>
  </div>`,
);

const ancestors = $('li').parents();
const ancestorsUntil = $('li').parentsUntil('div');

render(
  <>
    <p>
      Ancestor count (also includes "body" and "html" tags): {ancestors.length}
    </p>
    <p>Ancestor count (until "div"): {ancestorsUntil.length}</p>
  </>,
);
结果
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closest​

The closest method allows you to select the closest ancestor matching a given selector. It returns a new selection containing the closest ancestor element that matches the selector. If no matching ancestor is found, the method returns an empty selection.

Here's an example of using closest to select the closest ancestor <ul> element of a <li> element:

实时编辑器
const $ = cheerio.load(
  `<div>
    <ul>
      <li>Item 1</li>
    </ul>
  </div>`,
);

const list = $('li').closest('ul');
render(<>{list.prop('tagName')}</>);
结果
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Moving Sideways Within the DOM Tree​

Cheerio provides several methods for moving sideways within the DOM tree and selecting elements that are siblings of the current selection.

next and prev​

The next method allows you to select the next sibling element of a selection. It returns a new selection containing the next sibling element (if there is one). If the given selection contains multiple elements, next includes the next sibling for each one.

The prev method is similar to next, but allows you to select the previous sibling element. It returns a new selection containing the previous sibling element for each element in the given selection.

Here's an example of using next and prev to select sibling elements of a <li> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>Item 1</li>
    <li>Item 2</li>
  </ul>`,
);

const nextItem = $('li:first').next();
const prevItem = $('li:eq(1)').prev();

render(
  <>
    <p>Next: {nextItem.text()}</p>
    <p>Prev: {prevItem.text()}</p>
  </>,
);
结果
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nextAll, prevAll, and siblings​

The nextAll method allows you to select all siblings after the current element. It returns a new selection containing all sibling elements after each element in the current selection.

The prevAll method is similar to nextAll, but allows you to select all siblings before the current element. It returns a new selection containing all sibling elements before each element in the current selection.

The siblings method allows you to select all siblings of a selection. It returns a new selection containing all sibling elements of each element in the current selection.

Here's an example of using nextAll, prevAll, and siblings to select sibling elements of a <li> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>[1]</li>
    <li>[2]</li>
    <li>[3]</li>
  </ul>`,
);

const nextAll = $('li:first').nextAll();
const prevAll = $('li:last').prevAll();
const siblings = $('li:eq(1)').siblings();

render(
  <>
    <p>Next All: {nextAll.text()}</p>
    <p>Prev All: {prevAll.text()}</p>
    <p>Siblings: {siblings.text()}</p>
  </>,
);
结果
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nextUntil and prevUntil​

The nextUntil method allows you to select all siblings after the current element up to a specified sibling. It takes a selector or a sibling element as an argument and returns a new selection containing all sibling elements after the current element up to (but not including) the specified element.

The prevUntil method is similar to nextUntil, but allows you to select all siblings before the current element up to a specified sibling. It takes a selector or a sibling element as an argument and returns a new selection containing all sibling elements before the current element up to (but not including) the specified element.

Here's an example of using nextUntil and prevUntil to select sibling elements of a <li> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>Item 1</li>
    <li>Item 2</li>
    <li>Item 3</li>
  </ul>`,
);

const nextUntil = $('li:first').nextUntil('li:last-child');
const prevUntil = $('li:last').prevUntil('li:first-child');

render(
  <>
    <p>Next: {nextUntil.text()}</p>
    <p>Prev: {prevUntil.text()}</p>
  </>,
);
结果
Loading...

Filtering elements​

Cheerio provides several methods for filtering elements within a selection.

提示

Most of these filters also exist as selectors. For example, the first method is available as the :first selector. Users are encouraged to use the selector syntax when possible, as it is more performant.

eq​

The eq method allows you to select an element at a specified index within a selection. It takes an index as an argument and returns a new selection containing the element at the specified index.

Here's an example of using eq to select the second <li> element within a <ul> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>Item 1</li>
    <li>Item 2</li>
  </ul>`,
);

const secondItem = $('li').eq(1);
render(<>{secondItem.text()}</>);
结果
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filter and not​

The filter method allows you to select elements that match a given selector. It takes a selector as an argument and returns a new selection containing only those elements that match the selector.

The not method is similar to filter, but allows you to select elements that do not match a given selector. It takes a selector as an argument and returns a new selection containing only those elements that do not match the selector.

Here's an example of using filter and not to select <li> elements within a <ul> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li class="item">Item 1</li>
    <li>Item 2</li>
  </ul>`,
);

const matchingItems = $('li').filter('.item');
const nonMatchingItems = $('li').not('.item');

render(
  <>
    <p>Matching: {matchingItems.text()}</p>
    <p>Non-matching: {nonMatchingItems.text()}</p>
  </>,
);
结果
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has​

The has method allows you to select elements that contain an element matching a given selector. It takes a selector as an argument and returns a new selection containing only those elements that contain an element matching the selector.

Here's an example of using has to select <li> elements within a <ul> element that contain a <strong> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>Item 1</li>
    <li>
      <strong>Item 2</strong>
    </li>
  </ul>`,
);

const matchingItems = $('li').has('strong');
render(<>{matchingItems.length}</>);
结果
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first and last​

The first method allows you to select the first element in a selection. It returns a new selection containing the first element.

The last method is similar to first, but allows you to select the last element in a selection. It returns a new selection containing the last element.

Here's an example of using first and last to select elements within a <ul> element:

实时编辑器
const $ = cheerio.load(
  `<ul>
    <li>Item 1</li>
    <li>Item 2</li>
  </ul>`,
);

const firstItem = $('li').first();
const lastItem = $('li').last();

render(
  <>
    <p>First: {firstItem.text()}</p>
    <p>Last: {lastItem.text()}</p>
  </>,
);
结果
Loading...

Conclusion​

Cheerio provides a range of methods for traversing and filtering elements within a document. These methods allow you to move up and down the DOM tree, move sideways within the tree, and filter elements based on various criteria. By using these methods, you can easily select and manipulate elements within a document using Cheerio.