quilljs.js

var Delta = Quill.import('delta');
var quill = new Quill('#editor-container', {
  modules: {
    toolbar: true
  },
  placeholder: 'Compose an epic...',
  theme: 'snow'
});

// Store accumulated changes
var change = new Delta();
quill.on('text-change', function(delta) {
  change = change.compose(delta);
});

var a = new Delta().insert('a')
var b = new Delta().retain(1).insert('b')
var c = new Delta().retain(1).insert('c')
var x = a.compose(b).transform(c, true)

quill.updateContents(a, 'api')
quill.updateContents(b, 'api')
//quill.updateContents(c, 'api')
quill.updateContents(x, 'api')


console.log('a', a.compose(b))

console.log('x', x)