Optimisation for switch node

[namgk]

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimisation (improving load time for complex switch nodes from ~1.3 secs to ~0.6 secs )

Proposed changes

I usually have to work with complex switch nodes (>10 cases) and it is very slow whenever I open their configuration (~1-2 secs).

It seems it renders the typed fields eagerly, even without user interaction. It then chooses to hide and show certain DOM elements that were previously created based on the rule.

For complex switch node, this eager rendering results in tedious wait time even though the rules are very simple.

I'm proposing a simple lazy rendering of these fields to improve the load time of this node's configuration. Here we only render these fields on demand when the user choose to do so (e.g. select the rule).

With this approach, the performance could be significantly improved (tested with Chrome performance profiling, it improves load time for complex switch nodes from ~1.3 secs to ~0.6 secs ).

Checklist

• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the mailing list/slack team.
• I have run grunt to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality

[coveralls]

Coverage remained the same at 76.359% when pulling 0d680a5 on namgk:master into defa9a2 on node-red:master.

[knolleary]

Thanks for this.

Only one small change I'd suggest - to avoid the expense of throwing/catching an error.

[knolleary]

I've manually merged this into the dev branch - which is where new feature development lives - so I am going to close this PR.

In doing so I squashed a couple bugs I hit and also merged in some updates that had already been made in dev.

Thanks for this!