Execute automatically "Convert JSON to YAML" at start of Swagger Editor - json

Question

I am invoking a swagger json object per spec.js inside SwaggerEditorBundle to read local swagger api docs.
The swagger json code is bad formatting in one line inside Swagger Editor, so I need to click on Editor -> Convert JSON to YAML to enforce pretty formatting in YAML-style.
How to execute the javascript function automatically for Convert JSON to YAML after reading of spec.js to ensure always pretty formatting in YAML-style?
index.html
<script src="./dist/swagger-editor-bundle.js"> </script>
<script src="./dist/swagger-editor-standalone-preset.js"> </script>
<script src="./dist/spec.js"> </script>
<script>
window.onload = function() {
const editor = SwaggerEditorBundle({
spec: spec,
dom_id: '#swagger-editor',
layout: 'StandaloneLayout',
presets: [
SwaggerEditorStandalonePreset
]
})
window.editor = editor
}
</script>
spec.js
var spec = {
"consumes": [
"application/json"
],
"info": {
"title": "Simple API overview",
"version": "v2"
},
"paths": {
"/": {
"get": {
"operationId": "listVersionsv2",
"produces": [
"application/json"
],
"responses": {
"200": {
"description": "200 300 response",
"examples": {
"application/json": "{\n \"versions\": [\n {\n \"status\": \"CURRENT\",\n \"updated\": \"2011-01-21T11:33:21Z\",\n \"id\": \"v2.0\",\n \"links\": [\n {\n \"href\": \"http://127.0.0.1:8774/v2/\",\n \"rel\": \"self\"\n }\n ]\n },\n {\n \"status\": \"EXPERIMENTAL\",\n \"updated\": \"2013-07-23T11:33:21Z\",\n \"id\": \"v3.0\",\n \"links\": [\n {\n \"href\": \"http://127.0.0.1:8774/v3/\",\n \"rel\": \"self\"\n }\n ]\n }\n ]\n}"
}
}
},
"summary": "List API versions"
}
},
},
"swagger": "2.0"
}