Adding two empty arrays:
[] + []
results in an empty string. Why?
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The
+operator only exists for numbers and strings. When you use it on another type, JavaScript tries to convert the type (first to string, then int).When arrays are casts to strings, they are output as comma-separated strings.
So,
[] + []=>"" + ""=>"".Another example:
[1,2] + [3,4]=>"1,2" + "3,4"=>"1,23,4"Relevant Spec: https://tc39.es/ecma262/#sec-addition-operator-plus