Java Script if then statement

I am creating a form in Acrobat Pro where one page has a drop down field name "State". In the State drop down it lists all 50 states full names. On another page in the same form the user would like the previous choice of "State" to carry down, but only have the Abbreviations of the States. I am really new to Java Script, but what I attempted (shown below) only carries down the full State name. Anyone know how to fix this?

In this example I was trying to have the user Select Texas from above and in this field have TX show up. Instead Texas is entered automatically.

(function () {

     var I9 = this.getField("State").value;

if( State = "Texas") event.value = "TX";

})

Thanks in advance for your help.

Christy