The is join() function used to join the separator in the array.

Syntax: myArray.join(mySeparator);

The example as given below.

var alfabets = ["A", "B", "C", "D"];
//Join without seperator
var result1 = alfabets.join();//The output is A B C D.
//Join with seperator.
var result2 = alfabets.join(','); //The output is A, B, C, D.

The isNaN() function is used to CHECK the VALUE is not-a-number.

The example as given below

var var1 = isNaN(-1.23);//The output is false.
var VAR2 = isNaN(3);//The output is false.
var var3 = isNaN(0);//The output is false.
var var3 = isNaN("10/03/1984"); //The output is true.

The is join() function used to join the separator in the array.

Syntax: myArray.join(mySeparator);

The example as given below.

var alfabets = ["A", "B", "C", "D"];
//Join without seperator
var result1 = alfabets.join();//The output is A B C D.
//Join with seperator.
var result2 = alfabets.join(','); //The output is A, B, C, D.

The isNaN() function is used to check the value is not-a-number.

The example as given below

var var1 = isNaN(-1.23);//The output is false.
var var2 = isNaN(3);//The output is false.
var var3 = isNaN(0);//The output is false.
var var3 = isNaN("10/03/1984"); //The output is true.