SOURCE

var myEditor;
$(function() {
    ClassicEditor.create( document.querySelector( '#myEditor' ), {
        //  plugins: [ SourceEditing]
    } )
        .then( editor => {
                myEditor = editor;
            } )
        .catch( error => {
            console.error( error );
        } );
    $('#getBtn').click(function() {
        console.log("getData", myEditor.getData(), $("#myEditor").text());
    })
    $('#setBtn').click(function() {
        // var content = "<h1>&lt;script&gt;console.log('test')&lt;/script&gt;</h1>"
        // var content = "<script>alert('test')<\/script>"
        var content = "<script>console.log('test');<\/script>";
        myEditor.setData(content);
        // $("#myEditor").text("<script>console.log('test')<\/script>")
    })
});

<div>
    <div id="myEditor"></div>
    <button type="button" id="getBtn">get</button>
    <button type="button" id="setBtn">set</button>
</div>