Merge pull request doocs#52 from limbowandering/master

add javascript solutions

Author: yanglbme

solution/268.Missing Number/Solution.js

@@ -0,0 +1,3 @@
+const missingNumber = function(nums){
+  return (1 + nums.length)*nums.length/2 - nums.reduce((prev,cur)=>prev+=cur, 0);
+}

solution/326.Power of Three/Solution.js

@@ -0,0 +1,17 @@
+const isPowerOfThree1 = function(n){
+  return n <= 2? n === 1 : isPowerOfThree(n/3);
+};
+//44%;
+
+const isPowerOfThree2 = function(n){
+  const Max3PowerInt = 1162261467;
+  const MaxInt = 2147483647;
+  return n <= 0 || n > Max3PowerInt ? false: Max3PowerInt % n === 0;
+}
+//96%;
+
+const isPowerOfThree = function(n){
+  let t = Math.log10(n)/Math.log10(3);
+  return Number.isInteger(t);
+}
+//22%

solution/412.Fizz Buzz/Solution.js

@@ -0,0 +1,10 @@
+const fizzBuzz = function(n){
+  let arr = [];
+  for(let i = 1; i <= n; i++){
+    if(i % 15 === 0) arr.push('FizzBuzz');
+    else if(i % 3 === 0) arr.push('Fizz');
+    else if(i % 5 === 0) arr.push('Buzz');
+    else arr.push(`${i}`);
+  }
+  return arr;
+};