Changed from throwing strings to throwing custom subtypes of Error.

fraction.js

@@ -41,7 +41,7 @@
 
   "use strict";
 
-  // Maximum search depth for cyclic rational numbers. 2000 should be more than enough. 
+  // Maximum search depth for cyclic rational numbers. 2000 should be more than enough.
   // Example: 1/7 = 0.(142857) has 6 repeating decimal places.
   // If MAX_CYCLE_LEN gets reduced, long cycles will not be detected and toString() only gets the first 10 digits
   var MAX_CYCLE_LEN = 2000;
@@ -53,6 +53,24 @@
     "d": 1
   };
 
+  function createError(name) {
+      var errorConstructor = function() {
+        var temp = Error.apply(this, arguments);
+        temp.name = this.name = name;
+        this.stack = temp.stack;
+        this.message = temp.message;
+      }
+
+      var IntermediateInheritor = function() {};
+      IntermediateInheritor.prototype = Error.prototype;
+      errorConstructor.prototype = new IntermediateInheritor();
+
+      return errorConstructor;
+  }
+
+  var DivisionByZero = Fraction['DivisionByZero'] = createError('DivisionByZero');
+  var InvalidParameter = Fraction['InvalidParameter'] = createError('InvalidParameter');
+
   function assign(n, s) {
 
     if (isNaN(n = parseInt(n, 10))) {
@@ -62,7 +80,7 @@
   }
 
   function throwInvalidParam() {
-    throw "Invalid Param";
+    throw new InvalidParameter();
   }
 
   var parse = function(p1, p2) {
@@ -221,7 +239,7 @@
       }
 
     if (d === 0) {
-      throw "DIV/0";
+      throw new DivisionByZero();
     }
 
     P["s"] = s < 0 ? -1 : 1;
@@ -253,7 +271,7 @@
 
     // If we would like to compute really large numbers quicker, we could make use of Fermat's little theorem:
     // 10^(d-1) % d == 1
-    // However, we don't need such large numbers and MAX_CYCLE_LEN should be the capstone, 
+    // However, we don't need such large numbers and MAX_CYCLE_LEN should be the capstone,
     // as we want to translate the numbers to strings.
 
     var rem = 10 % d;
@@ -437,7 +455,7 @@
 
       parse(a, b);
       if (0 === P["n"] && 0 === this["d"]) {
-        Fraction(0, 0); // Throw div/0
+        Fraction(0, 0); // Throw DivisionByZero
       }
 
       /*
@@ -669,7 +687,7 @@
 
     /**
      * Returns an array of continued fraction elements
-     * 
+     *
      * Ex: new Fraction("7/8").toContinued() => [0,1,7]
      */
     'toContinued': function() {

tests/fraction.test.js

@@ -4,10 +4,10 @@ var Fraction = require('../fraction.min');
 
 var tests = [{
     set: "foo",
-    expect: "Invalid Param"
+    expectError: Fraction.InvalidParameter
   }, {
     set: " 123",
-    expect: "Invalid Param"
+    expectError: Fraction.InvalidParameter
   }, {
     set: 0,
     expect: 0
@@ -37,7 +37,7 @@ var tests = [{
     expect: "2.555"
   }, {
     set: " - ",
-    expect: "Invalid Param"
+    expectError: Fraction.InvalidParameter
   }, {
     set: ".5",
     expect: "0.5"
@@ -76,10 +76,10 @@ var tests = [{
     expect: "-123.(4)"
   }, {
     set: "0/0",
-    expect: "DIV/0"
+    expectError: Fraction.DivisionByZero
   }, {
     set: "9/0",
-    expect: "DIV/0"
+    expectError: Fraction.DivisionByZero
   }, {
     label: "0/1+0/1",
     set: "0/1",
@@ -104,7 +104,7 @@ var tests = [{
     expect: "-19.269(736842105263157894)"
   }, {
     set: "123.(22)123",
-    expect: "Invalid Param"
+    expectError: Fraction.InvalidParameter
   }, {
     set: "+33.3(3)",
     expect: "33.(3)"
@@ -113,13 +113,13 @@ var tests = [{
     expect: "3.(09009)"
   }, {
     set: "123.(((",
-    expect: "Invalid Param"
+    expectError: Fraction.InvalidParameter
   }, {
     set: "123.((",
-    expect: "Invalid Param"
+    expectError: Fraction.InvalidParameter
   }, {
     set: "123.()",
-    expect: "Invalid Param"
+    expectError: Fraction.InvalidParameter
   }, {
     set: null,
     expect: "0" // I would say it's just fine
@@ -294,7 +294,7 @@ var tests = [{
     set: 10,
     fn: "div",
     param: 0,
-    expect: "DIV/0"
+    expectError: Fraction.DivisionByZero
   }, {
     label: "-3 / 4",
     set: [-3, 4],
@@ -336,7 +336,7 @@ var tests = [{
     set: 0,
     fn: "inverse",
     param: null,
-    expect: "DIV/0"
+    expectError: Fraction.DivisionByZero
   }, {
     label: "abs(-100.25)",
     set: -100.25,
@@ -1095,32 +1095,29 @@ var tests = [{
 ];
 
 describe('Fraction', function() {
-
   for (var i = 0; i < tests.length; i++) {
 
     (function(i) {
+      var action;
 
       if (tests[i].fn) {
-
-        it(tests[i].label || tests[i].set, function() {
-          try {
-            assert.equal(new Fraction(tests[i].set)[tests[i].fn](tests[i].param).toString(), tests[i].expect);
-          } catch (e) {
-            assert.equal(e.toString(), tests[i].expect);
-          }
-        });
-
+        action = function() {
+          return new Fraction(tests[i].set)[tests[i].fn](tests[i].param).toString();
+        };
       } else {
-
-        it(tests[i].label || tests[i].set, function() {
-          try {
-            assert.equal(new Fraction(tests[i].set).toString(), tests[i].expect);
-          } catch (e) {
-            assert.equal(e.toString(), tests[i].expect);
-          }
-        });
+        action = function() {
+          return new Fraction(tests[i].set).toString();
+        };
       }
 
+      it(tests[i].label || tests[i].set, function() {
+        if(tests[i].expectError) {
+          assert.throws(action, tests[i].expectError);
+        } else {
+          assert.equal(action(), tests[i].expect);
+        }
+      });
+
     })(i);
   }
 });
@@ -1377,4 +1374,4 @@ describe('Fraction NaN', function() {
 
     })(i);
   }
-});
+});