add javascript solutions

Author: limbowandering

solution/020.Valid Parentheses/Solution.js

@@ -0,0 +1,14 @@
+const isValid = function(s){
+  let arr = [];
+  for(let i = 0; i < s.length; i++){
+    if(s[i] === '{' || s[i] === '[' || s[i] === '('){
+      arr.push(s[i]);
+    }else{
+      if(s[i] === ')' && arr[arr.length-1] === '(') arr.pop();
+      else if(s[i] === ']' && arr[arr.length-1] === '[') arr.pop();
+      else if(s[i] === '}' && arr[arr.length-1] === '{') arr.pop();
+      else return false;
+    }
+  }
+  return arr.length === 0;
+};

solution/190.Reverse Bits/Solution.js

@@ -0,0 +1,3 @@
+const reverseBits = function(n){
+  return parseInt(n.toString(2).split('').reverse().join('').padEnd(32,'0'),2);
+};

solution/461.Hamming Distance/Solution.js

@@ -0,0 +1,9 @@
+const hammingDistance = function(x,y){
+  let a = x ^ y;
+  a = a.toString(2);
+  let res = 0;
+  for(let i = 0 ; i < a.length; i++){
+    res += a[i] === '1';
+  }
+  return res;
+}