feat: add half task

package.json

@@ -16,7 +16,7 @@
     "url": "https://github.com/yankouskia/additional_6/issues"
   },
   "devDependencies": {
-    "mocha": "^3.2.0"
+    "mocha": "^6.2.0"
   },
   "homepage": "https://github.com/yankouskia/additional_6#readme"
 }

src/index.js

@@ -1,3 +1,49 @@
 module.exports = function zeros(expression) {
-  // your solution
+
+  partsOfExp = expression.split('*')
+
+  singleFactorials = []
+  doubleFactorials = []
+  partsOfExp.forEach(parseFactorial)
+  factorials = []
+  let result = BigInt(1)
+
+  function parseFactorial(item) {
+    if (item.match(/\d+!!/g)) {
+      doubleFactorials.push(Number(item.match(/\d+/g)))
+    } else {
+      singleFactorials.push(Number(item.match(/\d+/g)))
+    }
+  }
+
+  for (let index = 0; index < singleFactorials.length; index++) {
+    factorials.push(BigInt(doSingleFactorial(singleFactorials[index])))
+  }
+
+  for (let index = 0; index < doubleFactorials.length; index++) {
+    factorials.push(BigInt(doDoubleFactorial(doubleFactorials[index])))
+  }
+
+  function doSingleFactorial(number){
+    return (number != 1) ? number * doSingleFactorial(number - 1) : 1;
+  }
+  function doDoubleFactorial(number){
+    if (number % 2 === 0) {
+      return (number != 2) ? number * doDoubleFactorial(number - 2) : doSingleFactorial(2);
+    } else {
+      return (number != 1) ? number * doDoubleFactorial(number - 2) : 1;
+    }
+  }
+
+  console.log(factorials)
+  //multiply results 
+  for (let index = 0; index < factorials.length; index++) {
+    result *= BigInt(factorials[index])
+  }
+  console.log(result)
+  if (String(result).match(/[0]+\b/g) === null) {
+    return 0
+  } else {
+    return String(result).match(/[0]+\b/g)[0].length
+  }
 }