CODEWITHSUNDEEP
javascriptfunctionvariablesparameters
charlieyin
charlieyin

Reputation: 411

What is the point of having variable declarations in function parameters?

I stumbled upon a function that looked like this:

function pivot(arr, start = 0, end = arr.length){
  ...some code
}

Is this the same as writing:

function pivot(arr){
  let start = 0;
  let end = arr.length;
  ...some code
}

If so, are there any particular use cases in which declaring variables in the parameter of a function is advantageous other than for the sake of brevity?

Upvotes: 0

Views: 29

Answers (2)

ABGR
ABGR

Reputation: 5205

What you're seeing in this case is the Default Parameter. Here you can pass any values against these params, say start as 5 and end as 15. If you don't specify any values, the default values will be considered, i.e start as 0 and end as the length of arr

function pivot(arr, start = 0, end = arr.length){
  ...some code
}

On the other hand What you're seeing below is one variable declared (start) and another value (end) getting extracted from the parameter arr:

function pivot(arr){
  let start = 0;
  let end = arr.length;
  ...some code
}

Upvotes: 1

Jonathon Anderson
Jonathon Anderson

Reputation: 1200

What you're seeing in the function signature is parameters that have a default value. This allows you to pass some or all of the parameters at your discretion, while ensuring there is a usable value for each variable.

Upvotes: 1

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