Expose createTextVNode() 's functionality in the API

[green-coder]

What problem does this feature solve?

In the Vue Component's render() function, there is no normal way to create a VNode which represents naked text, same as what createTextVNode() would create.

This is needed when we want to generate things like:

<div>
  Hello <strong>Vue</strong>'s world.
</div>

What does the proposed API look like?

I propose to change the API in one of those 2 ways:

1. Add a behavior to the h function which is given to the user in the render() function so that it can be used for creating a 'text VNode', and document it. I propose to use the null or undefined on the first parameter.

2. Expose the createTextVNode() function (and why not also VNode()) somewhere inside Vue.

[green-coder]

Known 'hacky' workarounds:

1. Use a non-documented compiler method

render (h) {
  return this._v(val) // Works .. *for now*.
}

2. Use a poorly-documented method behavior's partial result.

render (h) {
  return h('p', val).children[0] // Works, but wastes CPU.
}

[yyx990803]

You can just provide raw text:

return h('div', [
  'Hello ',
  h('strong', 'Vue'),
  '\'s world.'
])

[green-coder]

That worked, thank you a lot.

You may want to add this information to documentation at https://vuejs.org/v2/guide/render-function.html#createElement-Arguments

Currently, the text say that the children should be VNodes.

[posva]

@green-coder that would be great, could you make a pr to https://github.com/vuejs/vuejs.org ?