Javascript 2つのFunction間でのvalueの引き継ぎ

<script type="text/javascript">
function validate(){
 　 var x = 2;
　  document.write(x + '\n'); //output: 2
 　 add(x)   //add()をCall
 　 console.log(x);　//output: 2
 　　}

 　function add(x){
　 var y = 1;
 　var z = x+y;
 　document.write(z); //output: 3
 　}

validate()
</script>

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もうひとつ、すごく苦労した受け渡し
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function startOver() {

 document.loan_form.loan_amt.value="0";
 document.loan_form.months.value="0";
 document.loan_form.rate.value="0";
 document.loan_form.extra.value="";
 document.getElementById("loan_info").innerHTML = "";
 document.getElementById("table").innerHTML = "";
}
function validate(){
 var loan_amt = document.loan_form.loan_amt.value;
 var months = document.loan_form.months.value;
 var rate = document.loan_form.rate.value;
 var extra = document.loan_form.extra.value;

 if(loan_amt <= 0 || isNaN(Number(loan_amt))){
  alert("please enter a valid loan amount.");
  document.loan_form.loan_amt.value = "0";
  }

 else if (months <=0 || parseInt(months) != months){
  alert("please enter a valid number of months.");
  document.loan_form.months.value = "0";
 }

 else if (rate <= 0 || isNaN(Number(rate))){
  alert("please enter a valid interest rate.");
  document.loan_form.loan_amt.value = "0";
  }

 else if (extra < 0 || isNaN(Number(extra))){
  alert("please enter a valid extra payment.");
  document.loan_form.loan_amt.value = "0";
 }

 else{
  alert("validation complete");


  alert(parseFloat(loan_amt) +'/n'+ parseInt(months))
  calculate(parseFloat(loan_amt),parseInt(months),parseFloat(rate),parseFloat(extra));
  // calculate function()に渡すvaluewを()内で指定
  //str型から其々の数字に
 }
}
function calculate(loan_amt,months,rate,extra){
 console.log(loan_amt + 1000 + 'hello'+ months + 'add' + rate+'extra'+extra);

}