Assigning String to Variable with If Else Statements

Question

sorry this is a super basic question, but I'm not too familiar with google script yet so finding answers to these simple tasks is proving to be difficult. In this code, I'm trying to set a string of numbers to a variable based on another variable. AppNaming is the variable I'm trying to assign the numbers to. AppType is already defined earlier in the code, and depending on the type, I need it to take only part of the variable AppNumber. Depending on the AppType, the AppNumber is separated by commas or slashes, hence the indexOf parts. Are if statements not allowed with var functions? I need the var AppNaming to change based on the AppType in order to name a file later on in the code. Thanks for all the help and sorry again if these questions are annoying; I'm still learning.

function AutoFill(e) {
 // variables all defined earlier 
 //Naming code
 var AppNaming = if( AppType == '1' ){ 
 AppNumber.substring( 0, AppNumber.indexOf(","))
 }
 else if ( AppType == '2'){
 AppNumber.substring( 0, AppNumber.indexOf("/"))
 }
 else ( AppType == '3'){
 AppNumber.substring( 0, AppNumber.indexOf(",")) 
}

Answer 1

You can only assign values to variables. Unfortunately, if statements are not values so you can't say var a = if (...) { } but you can say var a = 3

An if statement controls the flow of the application.

var something = 20;
var a;
if (something > 20) {
 a = "this block runs if something is greater than 20";
} else if (something < 20) {
 a = "this block runs if something is less than 20";
} else {
 a = "this block runs otherwise";
}
// The value of 'a' is 'this block runs otherwise' at this point

So in your example, you can assign App.Number.substring(0, AppNumber.indexOf(",") to a variable because that expression will return a value.

I would recommend you to learn the basics of JavaScript.