Merge pull request #287 from kriadmin/master

Add snippet primes

snippet-template.md

@@ -8,4 +8,4 @@ Explain briefly how the snippet works.
 const functionName = arguments =>
   {functionBody}
 // functionName(sampleInput) -> sampleOutput
-```
+```

snippets/primes.md

@@ -0,0 +1,16 @@
+### primes 
+
+Generates primes up to a given number, using the Sieve of Eratosthenes.
+
+Generate an array from `2` to the given number. Use `Array.filter()` to filter out the values divisible by any number from `2` to the square root of the provided number.
+
+```js
+const primes = num => {
+  let arr =  Array.from({length:num-1}).map((x,i)=> i+2), 
+    sqroot  = Math.floor(Math.sqrt(num)),
+    numsTillSqroot  = Array.from({length:sqroot-1}).map((x,i)=> i+2);
+  numsTillSqroot.forEach(x => arr = arr.filter(y => ((y%x)!==0)||(y==x)));
+  return arr; 
+}
+// primes(10) -> [2,3,5,7] 
+```