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new e80d10c4d3 issue #3539 : document JavaScript precision loss for large
integers (#7698)
e80d10c4d3 is described below
commit e80d10c4d324638cef0e896b9ff44e0c87762633
Author: Matt Casters <[email protected]>
AuthorDate: Thu Jul 30 21:07:54 2026 +0200
issue #3539 : document JavaScript precision loss for large integers (#7698)
---
.../ROOT/pages/pipeline/transforms/javascript.adoc | 30 +++++++++++++++++++++-
1 file changed, 29 insertions(+), 1 deletion(-)
diff --git
a/docs/hop-user-manual/modules/ROOT/pages/pipeline/transforms/javascript.adoc
b/docs/hop-user-manual/modules/ROOT/pages/pipeline/transforms/javascript.adoc
index 18dc9564cf..738d3d8c30 100644
---
a/docs/hop-user-manual/modules/ROOT/pages/pipeline/transforms/javascript.adoc
+++
b/docs/hop-user-manual/modules/ROOT/pages/pipeline/transforms/javascript.adoc
@@ -60,6 +60,7 @@ image:transforms/javascript-dialog.png[Javascript Transform
Dialog, width="90%"]
* The Get variables button may not always work, so enter variables manually.
* The JavaScript transform runs better with less whitespace and less line
continuations, especially when using GraphQL. Avoid multi-line expressions or
statements.
* Ensure you select the correct Type for the outgoing JavaScript fields.
+* Large integers (more than about 15–16 significant digits) can change when
they pass through the JavaScript transform. This is caused by JavaScript’s
internal floating-point number representation, not by Hop rounding. See
<<numeric-values, Numeric values>> below.
== Examples
E.g. JavasScript to create 4 new fields:
@@ -197,7 +198,7 @@ Fields must be added to the rows in the same order to keep
the structure of the
To add a field, define it as var in the Javascript pane, and add it as a field
in the Fields table.
-=== Numeric values
+=== [[numeric-values]]Numeric values
Most values that are assigned in JavaScript are floating point values by
default, even if you think you have assigned an integer value. If you are
having trouble using == or switch/case on values that you know are integers,
use the following constructs:
@@ -218,6 +219,33 @@ default:
}
----
+==== Loss of precision for large integers
+
+IMPORTANT: JavaScript numbers are always stored as double-precision
floating-point values (IEEE 754). That is a limitation of the language (and of
the Rhino engine Hop uses), not a bug in the transform.
+
+A double can represent integers exactly only up to `2^53 - 1`
(`Number.MAX_SAFE_INTEGER` = `9007199254740991`), which is about 15–16
significant digits. Hop Integer fields are 64-bit (`long`) and can hold larger
values. When such a value is passed into JavaScript—even if you only assign it
to another variable, log it, or convert it to a string—the engine converts it
through a floating-point number. Converting back to Integer (Integer → Double →
Integer) can change the least significant digits.
+
+For example:
+
+|===
+|Input Integer |Value after JavaScript
+
+|`1234567890123456` (16 digits)
+|`1234567890123456` (unchanged)
+
+|`12345678901234567` (17 digits)
+|`12345678901234568` (last digit changed)
+
+|`20231213084852358` (17 digits)
+|`20231213084852360` (last digits changed)
+|===
+
+Workarounds when you need full integer precision:
+
+* Keep large identifiers (order numbers, keys, barcodes, and similar) as
*String* fields and avoid treating them as numbers in JavaScript.
+* Prefer non-script transforms (Calculator, Formula, Select Values, and so on)
for numeric work when possible.
+* If you must use script for very large numbers, use the *Script* transform
(Groovy or another engine that supports arbitrary-precision types) instead of
the JavaScript transform, or pass values as strings and only convert them
outside JavaScript.
+
=== Filter Rows
To filter rows (remove the rows from the output for example) set the
pipeline_Status variable as follows:
