I need to create type of variable elem

Question

Example (doesn't work):
var elem = ['1','2'];
var elem.type = ['first','second','third'];

Answer 1

How about you make an object with fields value and type?

var elem = {
value: ['1', '2'],
type: ['first', 'second', 'third']
}
// ['1', '2']
console.log(elem.value);
// ['first', 'second', 'third']
console.log(elem.type);

Answer 2

You could use JavaScript object literal. A JavaScript object literal is a comma-separated list of name-value pairs wrapped in curly braces. Object literals encapsulate data, enclosing it in a tidy package.

Here an example:
var elem = {
number: ['1','2'],
type: ['first','second','third']
}

console.log(elem.number[0]);
console.log(elem.type[0]);
https://code.sololearn.com/WWSuV9CnRKWa/?ref=app