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.