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<title>CodeMirror: Version 4 upgrade guide</title>
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  <a href="https://codemirror.net"><h1>CodeMirror</h1><img id=logo src="logo.png"></a>

  <ul>
    <li><a href="../index.html">Home</a>
    <li><a href="manual.html">Manual</a>
    <li><a href="https://github.com/codemirror/codemirror">Code</a>
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    <li><a class=active href="#upgrade">Upgrade guide</a>
    <li><a href="#multisel">Multiple selections</a>
    <li><a href="#beforeSelectionChange">The beforeSelectionChange event</a>
    <li><a href="#replaceSelection">replaceSelection and collapsing</a>
    <li><a href="#changeEvent">change event data</a>
    <li><a href="#showIfHidden">showIfHidden option to line widgets</a>
    <li><a href="#module">Module loaders</a>
    <li><a href="#shareddata">Mutating shared data structures</a></li>
    <li><a href="#deprecated">Deprecated interfaces dropped</a>
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<article>

<h2 id=upgrade>Upgrading to version 4</h2>

<p>CodeMirror 4's interface is <em>very</em> close version 3, but it
does fix a few awkward details in a backwards-incompatible ways. At
least skim the text below before upgrading.</p>

<section id=multisel><h2>Multiple selections</h2>

<p>The main new feature in version 4 is multiple selections. The
single-selection variants of methods are still there, but now
typically act only on the <em>primary</em> selection (usually the last
one added).</p>

<p>The exception to this
is <a href="manual.html#getSelection"><strong><code>getSelection</code></strong></a>,
which will now return the content of <em>all</em> selections
(separated by newlines, or whatever <code>lineSep</code> parameter you passed
it).</p>

</section>

<section id=beforeSelectionChange><h2>The beforeSelectionChange event</h2>

<p>This event still exists, but the object it is passed has
a <a href="manual.html#event_beforeSelectionChange">completely new
interface</a>, because such changes now concern multiple
selections.</p>

</section>

<section id=replaceSelection><h2>replaceSelection's collapsing behavior</h2>

<p>By
default, <a href="manual.html#replaceSelection"><code>replaceSelection</code></a>
would leave the newly inserted text selected. This is only rarely what
you want, and also (slightly) more expensive in the new model, so the
default was changed to <code>"end"</code>, meaning the old behavior
must be explicitly specified by passing a second argument
of <code>"around"</code>.</p>

</section>

<section id=changeEvent><h2>change event data</h2>

<p>Rather than forcing client code to follow <code>next</code>
pointers from one change object to the next, the library will now
simply fire
multiple <a href="manual.html#event_change"><code>"change"</code></a>
events. Existing code will probably continue to work unmodified.</p>

</section>

<section id=showIfHidden><h2>showIfHidden option to line widgets</h2>

<p>This option, which conceptually caused line widgets to be visible
even if their line was hidden, was never really well-defined, and was
buggy from the start. It would be a rather expensive feature, both in
code complexity and run-time performance, to implement properly. It
has been dropped entirely in 4.0.</p>

</section>

<section id=module><h2>Module loaders</h2>

<p>All modules in the CodeMirror distribution are now wrapped in a
shim function to make them compatible with both AMD
(<a href="http://requirejs.org">requirejs</a>) and CommonJS (as used
by <a href="http://nodejs.org/">node</a>
and <a href="http://browserify.org/">browserify</a>) module loaders.
When neither of these is present, they fall back to simply using the
global <code>CodeMirror</code> variable.</p>

<p>If you have a module loader present in your environment, CodeMirror
will attempt to use it, and you might need to change the way you load
CodeMirror modules.</p>

</section>

<section id=shareddata><h2>Mutating shared data structures</h2>

<p>Data structures produced by the library should not be mutated
unless explicitly allowed, in general. This is slightly more strict in
4.0 than it was in earlier versions, which copied the position objects
returned by <a href="manual.html#getCursor"><code>getCursor</code></a>
for nebulous, historic reasons. In 4.0, mutating these
objects <em>will</em> corrupt your editor's selection.</p>

</section>

<section id=deprecated><h2>Deprecated interfaces dropped</h2>

<p>A few properties and methods that have been deprecated for a while
are now gone. Most notably, the <code>onKeyEvent</code>
and <code>onDragEvent</code> options (use the
corresponding <a href="manual.html#event_dom">events</a> instead).</p>

<p>Two silly methods, which were mostly there to stay close to the 0.x
API, <code>setLine</code> and <code>removeLine</code> are now gone.
Use the more
flexible <a href="manual.html#replaceRange"><code>replaceRange</code></a>
method instead.</p>

<p>The long names for folding and completing functions
(<code>CodeMirror.braceRangeFinder</code>, <code>CodeMirror.javascriptHint</code>,
etc) are also gone
(use <code>CodeMirror.fold.brace</code>, <code>CodeMirror.hint.javascript</code>).</p>

<p>The <code>className</code> property in the return value
of <a href="manual.html#getTokenAt"><code>getTokenAt</code></a>, which
has been superseded by the <code>type</code> property, is also no
longer present.</p>

</section>
</article>