Text selection commands for Cypress.io

selection-command.js

/**
 * Credits
 * @Bkucera: https://github.com/cypress-io/cypress/issues/2839#issuecomment-447012818
 * @Phrogz: https://stackoverflow.com/a/10730777/1556245
 *
 * Usage
 * ```
 * // Types "foo" and then selects "fo"
 * cy.get('input')
 *   .type('foo')
 *   .setSelection('fo')
 *
 * // Types "foo", "bar", "baz", and "qux" on separate lines, then selects "foo", "bar", and "baz"
 * cy.get('textarea')
 *   .type('foo{enter}bar{enter}baz{enter}qux{enter}')
 *   .setSelection('foo', 'baz')
 *
 * // Types "foo" and then sets the cursor before the last letter
 * cy.get('input')
 *   .type('foo')
 *   .setCursorAfter('fo')
 *
 * // Types "foo" and then sets the cursor at the beginning of the word
 * cy.get('input')
 *   .type('foo')
 *   .setCursorBefore('foo')
 *
 * // `setSelection` can alternatively target starting and ending nodes using query strings,
 * // plus specific offsets. The queries are processed via `Element.querySelector`.
 * cy.get('body')
 *   .setSelection({
 *     anchorQuery: 'ul > li > p', // required
 *     anchorOffset: 2 // default: 0
 *     focusQuery: 'ul > li > p:last-child', // default: anchorQuery
 *     focusOffset: 0 // default: 0
 *    })
 */

// Low level command reused by `setSelection` and low level command `setCursor`
Cypress.Commands.add('selection', { prevSubject: true }, (subject, fn) => {
  cy.wrap(subject)
    .trigger('mousedown')
    .then(fn)
    .trigger('mouseup');

  cy.document().trigger('selectionchange');
  return cy.wrap(subject);
});

Cypress.Commands.add('setSelection', { prevSubject: true }, (subject, query, endQuery) => {
  return cy.wrap(subject)
    .selection($el => {
      if (typeof query === 'string') {
        const anchorNode = getTextNode($el[0], query);
        const focusNode = endQuery ? getTextNode($el[0], endQuery) : anchorNode;
        const anchorOffset = anchorNode.wholeText.indexOf(query);
        const focusOffset = endQuery ?
          focusNode.wholeText.indexOf(endQuery) + endQuery.length :
          anchorOffset + query.length;
        setBaseAndExtent(anchorNode, anchorOffset, focusNode, focusOffset);
      } else if (typeof query === 'object') {
        const el = $el[0];
        const anchorNode = getTextNode(el.querySelector(query.anchorQuery));
        const anchorOffset = query.anchorOffset || 0;
        const focusNode = query.focusQuery ? getTextNode(el.querySelector(query.focusQuery)) : anchorNode;
        const focusOffset = query.focusOffset || 0;
        setBaseAndExtent(anchorNode, anchorOffset, focusNode, focusOffset);
      }
    });
});

// Low level command reused by `setCursorBefore` and `setCursorAfter`, equal to `setCursorAfter`
Cypress.Commands.add('setCursor', { prevSubject: true }, (subject, query, atStart) => {
  return cy.wrap(subject)
    .selection($el => {
      const node = getTextNode($el[0], query);
      const offset = node.wholeText.indexOf(query) + (atStart ? 0 : query.length);
      const document = node.ownerDocument;
      document.getSelection().removeAllRanges();
      document.getSelection().collapse(node, offset);
    })
    // Depending on what you're testing, you may need to chain a `.click()` here to ensure
    // further commands are picked up by whatever you're testing (this was required for Slate, for example).
});

Cypress.Commands.add('setCursorBefore', { prevSubject: true }, (subject, query) => {
  cy.wrap(subject).setCursor(query, true);
});

Cypress.Commands.add('setCursorAfter', { prevSubject: true }, (subject, query) => {
  cy.wrap(subject).setCursor(query);
});

// Helper functions
function getTextNode(el, match){
  const walk = document.createTreeWalker(el, NodeFilter.SHOW_TEXT, null, false);
  if (!match) {
    return walk.nextNode();
  }

  const nodes = [];
  let node;
  while(node = walk.nextNode()) {
    if (node.wholeText.includes(match)) {
      return node;
    }
  }
}

function setBaseAndExtent(...args) {
  const document = args[0].ownerDocument;
  document.getSelection().removeAllRanges();
  document.getSelection().setBaseAndExtent(...args);
}

This is awesome, thanks for sharing! I think you've got a vestigial nodes on line 101.

Any reason you can think of that these commands don't work properly in headless?

FYI, I couldn't get this working with input or textarea's and it looks like its due to lack of support: https://developer.mozilla.org/en-US/docs/Web/API/Window/getSelection#Related_objects (it also wasn't working in Chrome 80 for me), so I created a fork of the gist with a different path for those elements:
https://gist.github.com/samtsai/5cf901ba61fd8d44c8dd7eaa728cac49

This is old, here's our latest implementation as of this writing (you'll have to read a bit to pick out the relevant code): https://github.com/netlify/netlify-cms/blob/a4b7481a99f58b9abe85ab5712d27593cde20096/cypress/support/commands.js#L180

guys don't waste your time by trying to use the code. it throws the following error:
TypeError: Cannot read property 'wholeText' of undefined

@alexey-sh These functions are meant to be used with contenteditable not plain inputs thats why you are getting wholeText undefined error.

@kolpav thanks for the note, maybe you are right. but in the gist I can see

 * // Types "foo" and then sets the cursor at the beginning of the word
 * cy.get('input')
 *   .type('foo')
 *   .setCursorBefore('foo')

I guess 'input' selector means plain input.

does this (or the newer solution here in the comments) work on plain text in the DOM? (and not only on input)
for example if I have:
<p> this is the text I have <p>
can I select "is the"?

When I chain setSelection, setCursorBefore or setCursorAfter with .type() there is a 50/50 chance that .type() will occur first. Is there a way to fix this?

Thanks ! It works well for what I needed

guys don't waste your time by trying to use the code. it throws the following error: TypeError: Cannot read property 'wholeText' of undefined

@alexey-sh Were you able to solve this issue? I am facing the same. If you solved it, can you please tell me what changes did you make?

@rahulworks-git I don't remember exact way to solve it but I think it was fixed somehow. May by I decided to skip this kind of tests.