implementation with an example

Author: James Halliday

example/cmp.js

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+var equal = require('../');
+console.dir([
+    equal(
+        { a : [ 2, 3 ], b : [ 4 ] },
+        { a : [ 2, 3 ], b : [ 4 ] }
+    ),
+    equal(
+        { x : 5, y : [6] },
+        { x : 5, y : 6 }
+    )
+]);

index.js

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+var pSlice = Array.prototype.slice;
+var Object_keys = typeof Object.keys === 'function'
+    ? Object.keys
+    : function (obj) {
+        var keys = [];
+        for (var key in obj) keys.push(key);
+        return keys;
+    }
+;
+
+var deepEqual = module.exports = function (actual, expected) {
+  // 7.1. All identical values are equivalent, as determined by ===.
+  if (actual === expected) {
+    return true;
+
+  } else if (actual instanceof Date && expected instanceof Date) {
+    return actual.getTime() === expected.getTime();
+
+  // 7.3. Other pairs that do not both pass typeof value == 'object',
+  // equivalence is determined by ==.
+  } else if (typeof actual != 'object' && typeof expected != 'object') {
+    return actual == expected;
+
+  // 7.4. For all other Object pairs, including Array objects, equivalence is
+  // determined by having the same number of owned properties (as verified
+  // with Object.prototype.hasOwnProperty.call), the same set of keys
+  // (although not necessarily the same order), equivalent values for every
+  // corresponding key, and an identical 'prototype' property. Note: this
+  // accounts for both named and indexed properties on Arrays.
+  } else {
+    return objEquiv(actual, expected);
+  }
+}
+
+function isUndefinedOrNull(value) {
+  return value === null || value === undefined;
+}
+
+function isArguments(object) {
+  return Object.prototype.toString.call(object) == '[object Arguments]';
+}
+
+function objEquiv(a, b) {
+  if (isUndefinedOrNull(a) || isUndefinedOrNull(b))
+    return false;
+  // an identical 'prototype' property.
+  if (a.prototype !== b.prototype) return false;
+  //~~~I've managed to break Object.keys through screwy arguments passing.
+  //   Converting to array solves the problem.
+  if (isArguments(a)) {
+    if (!isArguments(b)) {
+      return false;
+    }
+    a = pSlice.call(a);
+    b = pSlice.call(b);
+    return deepEqual(a, b);
+  }
+  try {
+    var ka = Object_keys(a),
+        kb = Object_keys(b),
+        key, i;
+  } catch (e) {//happens when one is a string literal and the other isn't
+    return false;
+  }
+  // having the same number of owned properties (keys incorporates
+  // hasOwnProperty)
+  if (ka.length != kb.length)
+    return false;
+  //the same set of keys (although not necessarily the same order),
+  ka.sort();
+  kb.sort();
+  //~~~cheap key test
+  for (i = ka.length - 1; i >= 0; i--) {
+    if (ka[i] != kb[i])
+      return false;
+  }
+  //equivalent values for every corresponding key, and
+  //~~~possibly expensive deep test
+  for (i = ka.length - 1; i >= 0; i--) {
+    key = ka[i];
+    if (!deepEqual(a[key], b[key])) return false;
+  }
+  return true;
+}

package.json

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+{
+    "name" : "deep-equal",
+    "version" : "0.0.0",
+    "description" : "node's assert.deepEqual algorithm",
+    "main" : "index.js",
+    "directories" : {
+        "lib" : ".",
+        "example" : "example",
+        "test" : "test"
+    },
+    "scripts" : {
+        "test" : "tap test/*.js"
+    },
+    "devDependencies" : {
+        "tap" : "0.0.x"
+    },
+    "repository" : {
+        "type" : "git",
+        "url" : "http://github.com/substack/node-deep-equal.git"
+    },
+    "keywords" : [
+        "equality",
+        "equal",
+        "compare"
+    ],
+    "author" : {
+        "name" : "James Halliday",
+        "email" : "mail@substack.net",
+        "url" : "http://substack.net"
+    },
+    "license" : "MIT/X11",
+    "engine" : { "node" : ">=0.4" }
+}