What does the functional expression [] () {} mean? How does it work?

such as the title: when I was reading , an article about vuex , I found a code

.
[type.DONE_TODO](state,id){
    //...
}
What does the expression [] () {} mean by

? How does it work?

I made a bold conjecture based on ordinary function expressions:
[], which refers to an attribute variable of an object, combined with the following function expression writing, forms a variable function expression.
I wonder if that"s what it means?

Jun.29,2021

[type.DONE_TODO]src/vuex/modules/todo/mutation_type.js
(state,id) 
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