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std/http/etag.ts>ifNoneMatch

Deno standard library
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function ifNoneMatch
import { ifNoneMatch } from "https://deno.land/std@0.201.0/http/etag.ts";

A helper function that takes the value from the If-None-Match header and a calculated etag for the target entity and returns false if the etag for the entity matches the supplied value, otherwise true.

See MDN's If-None-Match article for more information on how to use this function.

import {
  calculate,
  ifNoneMatch,
} from "https://deno.land/std@0.201.0/http/etag.ts";
import { assert } from "https://deno.land/std@0.201.0/assert/assert.ts"

const body = "hello deno!";

Deno.serve(async (req) => {
  const ifNoneMatchValue = req.headers.get("if-none-match");
  const etag = await calculate(body);
  assert(etag);
  if (!ifNoneMatch(ifNoneMatchValue, etag)) {
    return new Response(null, { status: 304, headers: { etag } });
  } else {
    return new Response(body, { status: 200, headers: { etag } });
  }
});

Parameters

value: string | null
etag: string | undefined

Returns

boolean