Add all the A tasks

Task/Arithmetic-evaluation/JavaScript/arithmetic-evaluation.js

@@ -0,0 +1,55 @@
+function evalArithmeticExp(s) {
+  s = s.replace(/\s/g,'').replace(/^\+/,'');
+  var rePara = /\([^\(\)]*\)/;
+  var exp = s.match(rePara);
+
+  while (exp = s.match(rePara)) {
+    s = s.replace(exp[0], evalExp(exp[0]));
+  }
+  return evalExp(s);
+
+  function evalExp(s) {
+    s = s.replace(/[\(\)]/g,'');
+    var reMD = /\d+\.?\d*\s*[\*\/]\s*[+-]?\d+\.?\d*/;
+    var reM = /\*/;
+    var reAS = /-?\d+\.?\d*\s*[\+-]\s*[+-]?\d+\.?\d*/;
+    var reA  = /\d\+/;
+    var exp;
+
+    while (exp = s.match(reMD)) {
+      s = exp[0].match(reM)? s.replace(exp[0], multiply(exp[0])) : s.replace(exp[0], divide(exp[0]));
+    }
+
+    while (exp = s.match(reAS)) {
+      s = exp[0].match(reA)? s.replace(exp[0], add(exp[0])) : s.replace(exp[0], subtract(exp[0]));
+    }
+
+    return '' + s;
+
+    function multiply(s, b) {
+      b = s.split('*');
+      return b[0] * b[1];
+    }
+
+    function divide(s, b) {
+      b = s.split('/');
+      return b[0] / b[1];
+    }
+
+    function add(s, b) {
+      s = s.replace(/^\+/,'').replace(/\++/,'+');
+      b = s.split('+');
+      return Number(b[0]) + Number(b[1]);
+    }
+
+    function subtract(s, b) {
+      s = s.replace(/\+-|-\+/g,'-');
+
+      if (s.match(/--/)) {
+        return add(s.replace(/--/,'+'));
+      }
+      b = s.split('-');
+      return b.length == 3? -1 * b[1] - b[2] : b[0] - b[1];
+    }
+  }
+}