JavaScript / TypeScript

const response = await fetch(
  "https://api.unifyunits.com/v1/convert?value=1&from=ft&to=m",
  {
    headers: {
      Authorization: `Bearer ${process.env.UNIFYUNITS_API_KEY}`,
    },
  },
);

if (!response.ok) {
  const error = await response.json();
  throw new Error(`${error.error.code}: ${error.error.message}`);
}

const body = await response.json();
console.log(body.data.result.value); // "0.3048"

const response = await fetch("https://api.unifyunits.com/v1/batch", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.UNIFYUNITS_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    conversions: [
      { value: "10", from: "kg", to: "lb" },
      { value: "100", from: "km", to: "mi" },
    ],
  }),
});

const { data } = await response.json();

for (const item of data) {
  if (item.status === "success") {
    console.log(`Item ${item.index}: ${item.result.value} ${item.result.unit}`);
  } else {
    console.error(`Item ${item.index} failed: ${item.error.code}`);
  }
}

async function convert(value: string, from: string, to: string) {
  const url = new URL("https://api.unifyunits.com/v1/convert");
  url.searchParams.set("value", value);
  url.searchParams.set("from", from);
  url.searchParams.set("to", to);

  const res = await fetch(url, {
    headers: { Authorization: `Bearer ${process.env.UNIFYUNITS_API_KEY}` },
  });

  const body = await res.json();

  if (!res.ok) {
    switch (body.error.code) {
      case "UNKNOWN_UNIT":
        throw new Error("Unknown unit. Check GET /v1/units for valid IDs.");
      case "INCOMPATIBLE_UNITS":
        throw new Error(`Cannot convert between ${from} and ${to}.`);
      case "RATE_LIMIT_EXCEEDED":
        throw new Error("Rate limited. Retry after backoff.");
      default:
        throw new Error(`API error: ${body.error.code}`);
    }
  }

  return body.data.result.value;
}