Initialization

var's may be initialized optionally, if initialization is ommitted they are initialized to an empty string:

var x; // equivalent to var x = '';
var yMax = 12, message = 'hello world';

const initialization is mandatory (except for externs).

When initializing an array with a single value, all elements are set to that value:

var a1[100]; // all elements initialized to ''
const a2[12] = 100; // all elements set to 100

Array elements may be initialized similar to in C/C++ supplying the values in braces. There is a difference between global array initialization and array initialization within functions. The latter is dynamic while globals ar static.

Example:

var adr[4][2] = {
  { 1, 'fred' },
  { 2, "john" },
  { 3 }
};

If adr is a global array it's size is truely 4 by 2 as noted in the indexes. Not explicitly initialized elements are set to an empty string so adr will in fact show up like:

    1    'fred'
    2    'john'
    3    ''
    ''   ''

However if adr were a local var (declared within a function) the indexes are irrelevant; the number of dimensions and theire size is determined by the data itself. That will be an array of 3 rows and 2 columns in this case:

    1    'fred'
    2    'john'
    3    ''

Since the array indexes are irrelevant for initialized local arrays you may ommit them at all:

var adr = {
 { 1, 'fred' },
 { 2, 'john' },
 { 3, }
};