Add primeFactors

snippets/primeFactors.md

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+---
+title: primeFactors
+tags: math,algorithm,beginner
+---
+
+Finds the prime factors of a given number using the trial division algorithm.
+
+- Use a `while` loop to iterate over all possible prime factors, starting with `2`.
+- If the current factor, `f`, exactly divides `n`, add `f` to the factors array and divide `n` by `f`. Otherwise, increment `f` by one.
+
+```js
+const primeFactors = n => {
+  let a = [],
+    f = 2;
+  while (n > 1) {
+    if (n % f === 0) {
+      a.push(f);
+      n /= f;
+    } else {
+      f++;
+    }
+  }
+  return a;
+};
+```
+
+```js
+primeFactors(147); // [3, 7, 7]
+```