empty javascript array considered string?

Question

Is an empty JavaScript array considered a string? When I try to do an increment operation on an empty array it returns "1". I am also curious why it doesn't run the catch block.

let x=[]

try {
  x=x+1 
} catch(err){
  console.log(err)
}

console.log( typeof x, x);

Nope, the array is being coerced in to being a string by the `+` (concatenation) operator. — phuzi, Feb 22 '21 at 15:21
The + operator is not defined for arrays. What happens is that Javascript converts arrays into strings and concatenates those. — Hassan Imam, Feb 22 '21 at 15:21
Please have a read of https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Addition — evolutionxbox, Feb 22 '21 at 15:22
I feel like [this question](https://stackoverflow.com/questions/30875019/javascript-type-coercion-with-strings-and-indexing) might relate better — Dane Brouwer, Feb 22 '21 at 15:25

score 2 · Accepted Answer · answered Feb 22 '21 at 15:27

2

The + operator coerces the array and the number to a string first. This calls toString on the array, which calls join without any arguments, resulting in "". The result of concatenating "" and "1" is "1".

answered Feb 22 '21 at 15:27

Unmitigated

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Would it not be the result of concatenating `""` and `1`, rather than `"1"`? – Dane Brouwer Feb 22 '21 at 15:31
1

@DaneBrouwer Both operands are coerced to string first. – Unmitigated Feb 22 '21 at 15:32
okay i see now that both operands are converted to their primitives first. An object's primitive is it's default value, in this cast the array default method is `toString()`. Am I getting this right? – bfmcneill Feb 22 '21 at 17:15
1

@bfmcneill The `+` operator will coerce both operands to string if they are not both numbers. – Unmitigated Feb 22 '21 at 17:21

empty javascript array considered string?

1 Answers1