Question 179213 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – Mock new Date() in Deno

I’m wondering if anyone has been able to implement something like jest.spyOn(global, 'Date').mockImplementation(() => now); inside of Deno.

I have looked through the documentation for the mock in the Deno documentation here and I have looked through the mock time here however this doesn’t look like it will replace the new Date() with the mocked implementation.

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2

Answers


  1. 0

    You can overwrite any global variable directly — they’re accessible as properties/methods on globalThis.

    Here’s an example (that’s not specific to any testing framework) which replaces the global Date class with an example class that also has a method named toString:

    class Example {
  toString() {
    return "This is just an example";
  }
}

function overwriteDateAndReturnRestoreFn() {
  const originalDate = globalThis.Date;
  globalThis.Date = Example;
  return () => void (globalThis.Date = originalDate);
}

console.log(new Date().toString()); //=> <A string represetning the actual current date>

const restore = overwriteDateAndReturnRestoreFn();
console.log(new Date().toString()); //=> "This is just an example"

restore();
console.log(new Date().toString()); //=> <A string represetning the actual current date>
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