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jsNumber

jsNumber = 1

Example​

function ReadJSONDouble(Value: TJSONValue; var Number: Double): Boolean;
begin
  Result := (Value.ValueType = jsNumber) and Value.NotNull;
  if Result then
    Number := Value.AsDouble;
end;

Usage​

jsNumber identifies a JSON numeric value, with important exponent and Windows-locale limitations in Velox.

Parsing and formatting quirks​

Velox treats a numeric token as floating point only when it contains .. A standards-valid exponent-only token such as 1e3 is therefore treated as an integer and raises an error. Decimal parsing and output use the Windows decimal separator. On a computer using a comma, standard JSON input containing . can fail and output can contain ,, which is not a valid JSON decimal point.

Treat external or cross-locale numbers as untrusted. Use a standards-compliant JSON path when interoperable numeric syntax is required.

Additional Technical Info​

jsNumber is ordinal 1 of TJSONValueType. Both TJSONInteger (signed Int64 storage) and TJSONDouble (Delphi Double storage) receive this kind, so ValueType alone does not reveal integer versus floating representation.

Conversion boundaries​

AsDouble converts the textual form and is appropriate for either numeric subclass subject to locale/precision. AsInt64/AsInteger accept jsNumber, but a TJSONDouble with a fractional textual form is passed to integer parsing and raises. AsInteger can also overflow outside the 32-bit range. Binary Double cannot exactly represent every decimal or 64-bit integer.

A newly constructed numeric object is non-null zero. Clear marks it null without erasing stored data; clearing the null flag later can reveal the previous number. Null numeric accessors return zero, which is indistinguishable without checking IsNull.

The example is source-reviewed only; no JSON parsing, locale, precision, overflow, runtime or image test ran.

Related Code Library entries

External references

Created 2026-07-15