Polymer 2.0 element for Monaco Editor, a browser-based code editor that also powers Microsoft Visual Studio.

[ This description is mirrored from README.md at github.com/samie/monaco-editor on 2019-05-10 ]

monaco-editor GitHub release Published on webcomponents.org styled with prettier


<div slot="monaco-value">{
  "$schema": "https://vega.github.io/schema/vega-lite/v2.json",
  "description": "A simple bar chart with embedded data.",
  "data": {
    "values": [
      {"a": "A","b": 28}, {"a": "B","b": 55}, {"a": "C","b": 43},
      {"a": "D","b": 91}, {"a": "E","b": 81}, {"a": "F","b": 53},
      {"a": "G","b": 19}, {"a": "H","b": 87}, {"a": "I","b": 52}
  "mark": "bar",
  "encoding": {
    "x": {"field": "a", "type": "ordinal"},
    "y": {"field": "b", "type": "quantitative"}


bower install --save PolymerVis/monaco-editor

Documentation and demos

More examples and documentation can be found at monaco-editor webcomponents page.

The demos can be found at the monaco-editor Github page.

Special notes on styling and demo

The layout of the hints are out for the demo because of the way the original monaco editor is styled and the way webcomponents.org renders the demo. It is very difficult for me to isolate the conflicts.

You can still view the demo at the monaco-editor Github page.

Very important note on external dependencies when building/bundling your app

monaco-editor loads most of the required modules dynamically, hence polymer-build will not be able to properly detect these external modules. You will need to manually add bower_components/monaco-editor/node_modules/monaco-editor/min/vs/**/* into the extraDependencies to ensure these modules are exported together.

Important note on "hack" to allow Monaco Editor to work inside a custom element

Monaco Editor only works properly in the light DOM and there are a few functions that access or check on document.body. The selection is also dependent on document.caretPositionFromPoint or its variant. Hence, there are only a few solutions:

  • make a pull request and update the source code: but the source code seems to reside somewhere in Visual Studio Code repo instead of a proper monaco-editor-core repo,
  • attach the element (which Monaco Editor will be anchoring to) in the document.body, and try to sync the position, size, and style with the monaco-editor custom element,
  • create an iFrame and attach the iFrame to the monaco-editor custom element's shadowRoot.

The current approach now is, if the parent node of the monaco-editor is in the light DOM (it is not inside another custom element), the anchoring element will be insert as a slot (so that it remains in the light DOM), otherwise an iFrame will be created. In this case, a monaco, and editor proxy object will be created so that the some functions will be proxied into the iFrame.


PolymerVis is a personal project and is NOT in any way affliated with Microsoft, Polymer or Google.


monaco-editor is a Polymer 2.0 element for Monaco Editor, a browser-based code editor which also powers Visual Studio Code.

Quick start

<!-- enable code folding, minimap, and dark theme -->

Please look at the documentation for all the available options.

Pre-populated with codes

  1. Populate with the value property.
var codes = `// this is a comment line
var helloworld = "hello world";
<!-- 2-way binding is available for `value` -->
  1. Populate with a monaco-value slot element.
    Note that the text in the slot element is only loaded once during initialization. Subsequent changes to the slot will not change the value.
<!-- text is only loaded once, and not updated upon subsequent changes -->
  <div slot="monaco-value">// comment line
var helloworld = "hello world";</div>


monaco-schemas is a Polymer 2.0 element to where you can retrieve a list of JSON schemas through a space-separated key string. These schemas can then be passed into monaco-editor.

monaco-schemas currently only has the schemas for Vega v3.0 and Vega-Lite v2.0. However, you can easily add additional schemas into monaco-schemas.

<!-- extract `schemas` by definiting a space-separated string, `keys`. -->
<monaco-schemas keys="vega-lite" schemas="{{schemas}}"></monaco-schemas>

pass the `schemas` array to `json-schemas` and set `json-validate` flag
to enable hints, suggestions, and validation of the inputs.
<monaco-editor json-validate language="json"

You can define your own schemas by providing the uri to the schema. monaco-schemas will automatically retrieve the schema from the uri if the schema field is empty.

var data = {
  "vega-lite-uri": {
    "uri": "https://vega.github.io/schema/vega-lite/v2.json",
    "schema": null,
    "fileMatch": ["*"]
<!-- retrieve an array of schemas "vega-lite" and "vega-lite-uri". -->
<monaco-schemas keys="vega-lite vega-lite-uri"

You can also define a custom schema directly.

var data_w_cat = {
  "cat": {
    "schema": {
      "title": "Cat",
      "type": "object",
      "properties": {
        "name": {
          "description": "Name of the cat",
          "type": "string"
        "breed": {
          "description": "Breed of the cat",
          "type": "string"
        "age": {
          "description": "Age of the cat",
          "type": "string",
          "enum": ["kitten", "young adult", "adult", "old cat"]
    "fileMatch": ["*"]
<!-- retrieve custom schema "cat". -->
<monaco-schemas keys="cat"


Link to this version
ImportedReleased 27 April 2019MIT License
Framework Support
Polymer 2.0+
Browser Independent
Install with
bower install --save samie/monaco-editor"#2.0.5"
Run the above Bower command in your project folder. If you have any issues installing, please contact the author.
Release notes - Version 2.0.5


  • polymer#Polymer/polymer#^2.0.0
  • polymer-vis#PolymerVis/polymer-vis#^2.0.1