correctly handle the fact that nodeName is uppercase

[slimsag]

Fixes issue reported by @dmitshur in https://github.com/gopherjs/vecty/pull/249/files#r352319035

[slimsag]

@dmitshur thank you for reporting! I missed the fact that nodeName was uppercase. Would you be able to confirm if this fix works for you?

[slimsag]

panic: syscall/js: call of Value.Call on string

Ah, this actually appears to be an incorrect limitation of GOOS=js GOARCH=wasm in at least Go 1.12 and perhaps also in master -- I think this program does not work except under GopherJS: https://gopherjs.github.io/playground/#/UxD9vDjbf0

[codecov-io]

Codecov Report

Merging #251 into master will increase coverage by 0.12%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #251      +/-   ##
==========================================
+ Coverage   59.31%   59.43%   +0.12%     
==========================================
  Files           4        4              
  Lines         671      673       +2     
==========================================
+ Hits          398      400       +2     
  Misses        215      215              
  Partials       58       58

Impacted Files	Coverage Δ
dom.go	57.42% <100%> (ø)	⬆️
dom_native.go	52.94% <100%> (+6.27%)	⬆️

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[dmitshur]

Do you have a way of checking whether performance is impacted doing this on each toLower call, compared to:

func toLower(s string) string {
    return toLowerCase.Call("call", js.ValueOf(s)).String()
}

var toLowerCase = js.Global().Get("String").Get("prototype").Get("toLowerCase")

Also, the string -> js.Value -> string conversions can be short-circuited if you're willing to create a more dedicated helper for getting the node name, for example:

// +build js
func lowerNodeName(node jsObject) string {
    return toLowerCase.Call("call", node.Get("nodeName")).String()
}

// +build !js
func lowerNodeName(node jsObject) string {
    return strings.ToLower(node.Get("nodeName").String())
}

I don't have a sense whether the performance difference would be significant or negligible.

If performance isn't a bottneck or priority for now, this can all be considered later of course.

[slimsag]

I think even if performance of this is poor, it would probably be negligible AND since it only occurs on calls to RenderBody, RenderInto, RenderIntoNode it is not very frequently called, so as-is is probably fine for now.

Benchmarking things overall (all of Vecty) would definitely be a good idea, though that will probably come a bit later.