You can declare a variable by the var statement such as:

var strname = some value

You can also declare a variable with simply assigning a value to the variable. Although, if you do not assign a value & simply employ the variable then it leads to an error.

Strname = some value

You can assign a value to a variable as:

var strname = "Hello"

Or

strname = "Hello"

The variable name is onto the left hand side of the expression & the value you desired to assign to variable is on to the right side. Therefore the variable "strname" illustrated above gets the value "Hello" assigned to it.