I am having difficulty with if statements in this code. When I first tried it - it worked as expected. Is their a simpler way to write this and does anyone know of a good text book that I can get to help me improve my skills

// Sets variables for the entire document and Automatically Populates certain variable based in inputs throughout the document.;

// Assigns variables for populating the rest of the document;

var ord = this.getField("Order").valueAsString;
var bol = this.getField("BOL").valueAsString;
var trac = this.getField("Tractor").valueAsString;
var trail = this.getField("Trailer").valueAsString;
var lead = this.getField("Lead").valueAsString;
var lpay = this.getField("LPay").valueAsString;
var team = this.getField("Team").valueAsString;
var tpay = this.getField("TPay").valueAsString;
var lead1 = this.getField("Lead1").valueAsString;
var lpay1 = this.getField("LPay1").valueAsString;
var team1 = this.getField("Team1").valueAsString;
var tpay1 = this.getField("TPay1").valueAsString;
var olec = this.getField("OLEC").valueAsString;
var trail1 = this.getField("Trailer1").valueAsString;
var refin = this.getField("Refinery").valueAsString;
var unit = this.getField("Unit").valueAsString;
var tmt = this.getField("TMT").value;
var tmt1 = this.getField("TMT1").value;

// Ensures that global variables do not have a values until certain conditions are met;

var ptrip = 0;
var ptrip1 = 0;
var drop = 0;
var drop1 = 0;
var hose = 0;
var border = 0;
var border1 = 0;
var mile = 0;
var mile1 = 0;
var local = 0;
var local1 = 0;
var ldr = 0;
var ldr1 = 0;
var ttpay = 0;
var ttpay1 = 0;

event.value = "";

if (lead.value !== null || lead.value !=="") {

      if (team.value !== null || team.value !== "") {

            if (lead1.value == null || lead1.value == "") {

               event.value=team;
               var tpayz = tpay;
               var ptrip = 9.45;
               var ptrip1 = 9.45;
               var drop = 9.45;
               var drop1 = 9.45;
               var hose = 10.50;
               var border = 78.75;
               var border1 = 78.75;
               var mile = .305;
               var mile1 = .305;
               var ldr = tmt;
               var ldr1 = tmt;
}
           if ((lead1.value !== null || lead1.value !== "")&&(team1.value == null || team1.value == "")) {

               event.value=lead1;
               var tpayz = lpay1;
               var ptrip = 9.45;
               var ptrip1 = 18.9;
               var drop = 9.45;
               var drop1 = 18.9;
               var hose = 10.5;
               var border = 78.75;
               var border1 = 157.50;
               var mile = .305;
               var mile1 = .483;
               var ldr = tmt;
               var ldr1 = tmt1;
}

        if ((lead1.value !== null || lead1.value !== "")&&(team1.value !== null || team1.value !== "")) {

               event.value=lead1;
               var tpayz = lpay1;
               var ptrip = 9.45;
               var ptrip1 = 9.45;
               var drop = 9.45;
               var drop1 = 9.45;
               var hose = 10.5;
               var border = 78.75;
               var border1 = 78.75;
               var mile = .305;
               var mile1 = .305;
               var ldr = tmt;
               var ldr1 = tmt1;
}}

      if (team.value == null || team.value == "") {

            
         if ((lead1.value !== null || lead1.value !== "")&&(team1.value == null || team1.value == "")) {

               event.value=lead1;
               var tpayz = lpay1;
               var ptrip = 18.9;
               var ptrip1 = 18.9;
               var drop = 18.9;
               var drop1 = 18.9;
               var hose = 10.5;
               var border = 157.5;
               var border1 = 157.50;
               var mile = .483;
               var mile1 = .483;
               var ldr = tmt;
               var ldr1 = tmt1;
}

         if ((lead1.value !== null || lead1.value !== "")&&(team1.value !== null || team1.value !== "")) {

               event.value=lead1;
               var tpayz = lpay1;
               var ptrip = 18.9;
               var ptrip1 = 9.45;
               var drop = 18.9;
               var drop1 = 9.45;
               var hose = 10.5;
               var border = 157.5;
               var border1 = 78.75;
               var mile = .483;
               var mile1 = .305;
               var ldr = tmt;
               var ldr1 = tmt1;
}}}