[SOLVED] `op run --` does not conceal value when do writeFile in nodejs

When I do writeFile into stdout/stderr, it just prints out the value. If I just do console.log(process.env.GITHUB_USERNAME), the value is concealed. Here's the source code:

require("dotenv").config();
const process = require("process");
const fs = require("fs");

fs.writeFileSync(0, process.env.GITHUB_USERNAME);

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1Password Version: 8.10.6
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OS Version: macOS 13.3.1(a)
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