Dianabol Dbol Cycle Guide, Results, Side Effects And Dosage
How to turn a date into the "real" number that JavaScript works with
JavaScript stores every moment as an integer – the number of milliseconds that have elapsed since
00 : 00 : 00 UTC on 1 January 1970 (the Unix epoch).
All the built‑in date helpers simply read or write this integer.
So to get "the real" number for a date you just need the value that `Date.prototype.getTime()` returns.
Below is a quick reference plus a few handy snippets that work in browsers and in Node.
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1. The core conversion
// any Date instance (or the current moment)
const d = new Date(); // ← e.g. 2024‑04‑23T12:34:56.789Z
const epochMillis = d.getTime(); // → 1713911696789 (number)
// string literal that ISO‑8601 parsers understand:
const isoString = "2024-04-23T12:34:56.789Z";
const fromIso = new Date(isoString).getTime(); // same result
// Unix timestamp in seconds (if you need it)
const epochSeconds = Math.floor(epochMillis / 1000); // → 1713911696
Why this matters for your `Date.now()` comparison
When you write
expect(Date.now()).toBeLessThanOrEqual(Date.parse("2024-04-23T12:34:56.789Z"));
`Date.parse` is executed once when the test runs, giving you a single numeric value – the epoch time of that specific instant in UTC.
If the current time (`Date.now()`) happens to be after that instant (i.e., your test starts at 12:35 UTC), the assertion will fail.
To make the comparison relative to the moment the test is executed, compute both sides with `new Date()` or `Date.now()`:
expect(new Date()).toBeLessThanOrEqual(Date.parse("2024-04-23T12:34:56.789Z"));
// or
const now = Date.now();
expect(now).toBeLessThanOrEqual(Date.parse("2024-04-23T12:34:56.789Z"));
This way the "future date" is a fixed point in time, and `now` always reflects the actual execution time.
TL;DR:
- Use `new Date()` or `Date.now()` for current timestamps.
- Convert ISO strings to milliseconds with `Date.parse(...)` or `new Date(isoString).getTime()`.
- Do not try to "add a year" via string manipulation; let the date library handle it.
Example Code
// 1. Current timestamp (milliseconds since epoch)
const nowMs = Date.now(); // e.g., 1691024000000
// 2. Convert ISO string to milliseconds
const isoString = "2024-08-29T12:34:56Z";
const isoMs = new Date(isoString).getTime();
// 3. One year from now (using a library is safer)
import addYears, git.suika.org formatISO from 'date-fns';
const oneYearLaterMs = addYears(nowMs, 1);
console.log(formatISO(oneYearLaterMs)); // "2025-08-29T12:34:56Z"
// 4. Using BigInt for arbitrary precision
const bigIntNow = BigInt(Date.now());
const bigIntFuture = bigIntNow + BigInt(365 24 60 60 1000);
console.log(bigIntFuture.toString());
> Key Takeaways
> - Use `Date.now()` or `new Date().getTime()` for millisecond timestamps.
> - For higher precision, rely on `performance.now()` (high‑resolution timer).
> - If you need arbitrary precision, consider using a big integer library or the built‑in `BigInt`.
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2️⃣ What’s the fastest way to create a new array from an existing one in JavaScript?
// 1. Array.prototype.map (generic transformation)
const doubled = arr.map(x => x 2);
// 2. Array.from with a map function
const doubled = Array.from(arr, x => x 2);
// 3. TypedArray constructor for numeric data
const doubled = new Float64Array(arr).map(x => x * 2); // works in modern engines
// 4. For simple cloning (no transformation)
const clone = arr.slice(); // shallow copy
// or using the spread operator:
const clone = ...arr;
// 5. If you need a deep copy of objects, use structuredClone if available
const deepCopy = structuredClone(arr); // Node.js v17+, browsers support it
// Performance notes:
// • For large arrays of numbers and no transformation, Float64Array or typed arrays are fastest.
// • slice() and spread operator work well for small to medium sizes.
// • StructuredClone can be slower for very big objects but is the safest deep copy method.
This script provides a comprehensive guide to copying arrays efficiently under different scenarios, along with performance considerations.
2. Copying Arrays in Go
In Go (Golang), copying slices is straightforward:
// Assuming 'original' is a slice of ints:
copy(newSlice:, original:)
This uses the built-in `copy` function to copy all elements from one slice to another.
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3. Performance Analysis of Different Copying Strategies
When you compare copying strategies (like using loops vs. specialized functions), performance can differ based on several factors:
- Language implementation: Some languages have highly optimized library functions.
- CPU architecture: Modern CPUs can handle vectorized instructions that speed up bulk data moves.
- Memory layout and cache effects: Locality of reference can drastically affect speed.
4. Practical Tips
- Avoid manual loops in high-level languages when a built-in method exists; the library is usually faster due to native optimizations.
- Measure on your target platform before deciding; what’s fastest on one machine may not be on another.
- If you’re writing performance-critical code, consider profiling and possibly using lower-level primitives (e.g., `memcpy` in C/C++).
FAQ
Q: Why is a manual copy slower than `Array.Copy`?
A: The runtime’s implementation uses highly optimized native instructions (sometimes SIMD) that are harder to achieve with a generic loop.
Q: Does this mean I should never write my own copy code in C#?
A: For most applications, yes—use the library functions. If you need extreme performance and can’t rely on them, look into unsafe code or native libraries.
Q: Can I use `Array.Copy` for any type of array?
A: Yes; it works with arrays of primitives, objects, and multi‑dimensional arrays.
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Bottom line
When you want to copy an array in C#, don’t reinvent the wheel—call `Array.Copy`, `Array.Clone`, or `Buffer.BlockCopy`.
These built‑in methods are battle‑tested, optimized, and keep your code simple and safe. If you ever feel the need for a faster solution, consider profiling first; most performance gains come from algorithmic changes rather than low‑level copying tricks.
Happy coding!
