如何使用 Javascript 计算 Acrobat PDF 中的字段？

Question

Calculating fields Acrobat pdf Javascript the total amount displays incorrectly when I skip a field but It works correctly when each field has a value from top to down. What is wrong?

var fields = this.getField("amount");
var a = fields.getArray();
var sum = 0;
for (i = 0; i < a.length; i++){
sum += a[i].value;

//I tried to place zeros in the fields if there are no values
if (fields.value == null){
   fields.value = 0;
}
}
//This code accept the total amount and also hides the default zeros 
if (sum > 0){
    event.value = sum;
}

else {
    event.value = "";
}

Answer 1

In such a loop, before adding up the running total, I usually check whether a field has a value by comparing its value with its defaultValue . The line looks like this:

if (this.getField("myField").value != this.getField("myField").defaultValue) {

Normally, comparing on value level is sufficient, but if 0 is a legal value, the comparison has to include the type. Then it looks like this:

if (this.getField("myField").value !== this.getField("myField").defaultValue) {

And that should do it.

Answer 2

To fixed this, Javascript Addition operator ``+``` can also be used to add (concatenate) strings. The empty field was acting as string so you will need to escape the string by appending + to the values.

sum += +a[i].value;

It is the same as var fields = +this.getField("amount");