what is declaration?

Answer 1

In JavaScript you 'Declare' a variable with the 'var' keyword so:

var random = "number";

Answer 2

declaring a variable to class like
int a:
here a is declared for int class(data type)

Answer 3

Declaration of array
"Data type" "array name" "size"
Int array[10];
You can also gives the value like
Int array[10] = {1,2,3,4,5,6,7,8,9,10};