Additional snippets

snippets/RGB-to-hexadecimal.md

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+## RGB to hexadecimal
+
+Convert each value to a hexadecimal string, using `toString(16)`, then `padStart(2,'0')` to get a 2-digit hexadecimal value.
+Combine values using `join('')`.
+
+```js
+var rgbToHex = (r, g, b) =>
+  [r.toString(16).padStart(2,'0') , g.toString(16).padStart(2,'0') , b.toString(16).padStart(2,'0')].join('');
+```

snippets/even-or-odd-number.md

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+### Even or odd number
+
+Use `Math.abs()` to extend logic to negative numbers, check using the modulo (`%`) operator.
+Return `true` if the number is even, `false` if the number is odd.
+
+```js
+var isEven = num => Math.abs(num) % 2 === 0;
+```

snippets/greatest-common-divisor-gcd.md

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+## Greatest common divisor (GCD)
+
+Use recursion.
+Base case is when `y` equals `0`. In this case, return `x`.
+Otherwise, return the GCD of `y` and the remainder of the division `x/y`.
+
+```js
+var gcd = (x , y) => !y ? x : gcd(y, x % y);
+```

snippets/sum-of-array-of-numbers.md

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+### Sum of array of numbers
+
+Use `reduce()` to add each value to an accumulator, initialized with a value of `0`.
+
+```js
+var sum = arr =>
+  arr.reduce( (acc , val) => acc + val, 0);
+```

snippets/unique-values-of-array.md

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+### Unique values of array
+
+Use `reduce()` to accumulate all unique values in an array.
+Check if each value has already been added, using `indexOf()` on the accumulator array.
+
+```js
+var uniqueValues = arr =>
+  arr.reduce( (acc, val) => {
+    if(acc.indexOf(val) === -1)
+      acc.push(val);
+      return acc;
+  }, []);
+```