Syntax - what does square brackets around a variable declaration mean [duplicate]

问题

This question already has answers here:

Multiple assignment in javascript? What does [a,b,c] = [1, 2, 3]; mean? (4 answers)

Closed 2 years ago.

Take the following line of code

const [component] = router.getMatchedComponents({ ...to })

Could anyone advise what the square brackets around component means here? I have tried to google this but struggling to find an answer

回答1:

It's called Destructuring assignment, and it's used to unpack the values of an array and assign them to new variables.

So here in your code:

const [component] = router.getMatchedComponents({ ...to })

You are assigning to the component variable the first element held in the array that will be returned by router.getMatchedComponents({...to}), where to is an array-like structure turned into object using the spread operation.

来源：https://stackoverflow.com/questions/47287635/syntax-what-does-square-brackets-around-a-variable-declaration-mean