[Bug][http-client-js] ser/deser for unixTimestamp type has issues

[MaryGao]

Describe the bug

Ser/deser for unixTimestamp type has issues

Reproduction

NA

Checklist

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• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.