Javascript converting from string to instance name

Question

I have a string representing the name of a tool in a screen painting application (examples: 'pencil', 'marker', 'line', 'rect'). For each tool, I have defined a class to perform that tool's functions (e.g. PencilHandler) and created an instance of it (e.g. pencilHandler = new PencilHandler()). Currently, I use a long switch statement to go from the name of the tool (a string) to the corresponding instance (an object) (e.g. switch(tool) { case 'pencil': return pencilHandler; ...}) and then call a method of the returned instance (e.g. pencilHandler.mousedown(event)).

It would be neater if I could dynamically construct the instance name from the tool name rather than using the switch statement, but I haven't been able to find out how to do this. For instance, tool + 'Handler'[mousedown](event) doesn't work (gives a TypeError).

You want to store your instances in a Map by their name.

Bergi
– Bergi

2020-06-16 13:34:57 +00:00
Commented Jun 16, 2020 at 13:34 — Bergi
– Bergi, Commented Jun 16, 2020 at 13:34

Dmitry Reutov · Accepted Answer · 2020-06-16 13:40:44Z

1

collect them in one object and call by key name

const classesCollection = { PencilHandler, ErazerHandler, BrushHandler }
const requiredClass = classesCollection[tool + 'Handler]

answered Jun 16, 2020 at 13:40

Dmitry Reutov

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