JavaScript object deep comparison. Comparing x === y, where x and y are values, return true or false. Comparing x === y, where x and y are objects, returns true if x and y refer to the same object. Otherwise, returns false even if the objects appear identical. Here is a solution to check if two objects are the same.

1_primitive_comparison.js

//Primitive Type Comparison
var a = 1;
var b = 1;
var c = a;

console.log(a == b);  //true
console.log(a === b); //true
console.log(a == c);  //true
console.log(a === c); //true

2_obeject_comparison.js

//Object comparison
var a = { blah: 1 };
var b = { blah: 1 };
var c = a;

console.log(a == b);    //false
console.log(a === b);   //false
console.log(a == c);	  //true
console.log(a === c);   //true

object.compare.js

//How To Compare Object Values
var a = { blah: 1 };
var b = { blah: 1 };
var c = a;
var d = { blah: 2 };

Object.compare = function (obj1, obj2) {
	//Loop through properties in object 1
	for (var p in obj1) {
		//Check property exists on both objects
		if (obj1.hasOwnProperty(p) !== obj2.hasOwnProperty(p)) return false;
 
		switch (typeof (obj1[p])) {
			//Deep compare objects
			case 'object':
				if (!Object.compare(obj1[p], obj2[p])) return false;
				break;
			//Compare function code
			case 'function':
				if (typeof (obj2[p]) == 'undefined' || (p != 'compare' && obj1[p].toString() != obj2[p].toString())) return false;
				break;
			//Compare values
			default:
				if (obj1[p] != obj2[p]) return false;
		}
	}
 
	//Check object 2 for any extra properties
	for (var p in obj2) {
		if (typeof (obj1[p]) == 'undefined') return false;
	}
	return true;
};

console.log(Object.compare(a, b));  //true
console.log(Object.compare(a, c));  //true
console.log(Object.compare(a, d));  //false

+1 like on the solution of @DLiblik posted above, which also covers dates and functions. Maybe post it in a separate github repository so it can be found more easily?

Always glad to see this old thing created in 2013 has got people talking and learning from each other.

Best implementation that I have seen so far is in rambda's "equals" function.

The only thing that I think can be improved (although, I am not sure that this is the right direction) is when both arguments have a "function" type, we could convert the source code to strings and compare them...

Here is the code (I simply put everything into 1 file) from their source:

const _isArray = Array.isArray;

function type(input) {
  const typeOf = typeof input;

  if (input === null) {
    return "Null";
  } else if (input === undefined) {
    return "Undefined";
  } else if (typeOf === "boolean") {
    return "Boolean";
  } else if (typeOf === "number") {
    return Number.isNaN(input) ? "NaN" : "Number";
  } else if (typeOf === "string") {
    return "String";
  } else if (_isArray(input)) {
    return "Array";
  } else if (typeOf === "symbol") {
    return "Symbol";
  } else if (input instanceof RegExp) {
    return "RegExp";
  }

  const asStr = input && input.toString ? input.toString() : "";

  if (["true", "false"].includes(asStr)) return "Boolean";
  if (!Number.isNaN(Number(asStr))) return "Number";
  if (asStr.startsWith("async")) return "Async";
  if (asStr === "[object Promise]") return "Promise";
  if (typeOf === "function") return "Function";
  if (input instanceof String) return "String";

  return "Object";
}

function parseError(maybeError) {
  const typeofError = maybeError.__proto__.toString();
  if (!["Error", "TypeError"].includes(typeofError)) return [];

  return [typeofError, maybeError.message];
}

function parseDate(maybeDate) {
  if (!maybeDate.toDateString) return [false];

  return [true, maybeDate.getTime()];
}

function parseRegex(maybeRegex) {
  if (maybeRegex.constructor !== RegExp) return [false];

  return [true, maybeRegex.toString()];
}


// main function is here
function equals(a, b) {
  if (arguments.length === 1) return (_b) => equals(a, _b);

  const aType = type(a);
  if (aType !== type(b)) return false;
  if (aType === "Function") {
    return a.name === undefined ? false : a.name === b.name;
  }

  if (["NaN", "Undefined", "Null"].includes(aType)) return true;

  if (aType === "Number") {
    if (Object.is(-0, a) !== Object.is(-0, b)) return false;

    return a.toString() === b.toString();
  }

  if (["String", "Boolean"].includes(aType)) {
    return a.toString() === b.toString();
  }

  if (aType === "Array") {
    const aClone = Array.from(a);
    const bClone = Array.from(b);

    if (aClone.toString() !== bClone.toString()) {
      return false;
    }

    let loopArrayFlag = true;
    aClone.forEach((aCloneInstance, aCloneIndex) => {
      if (loopArrayFlag) {
        if (
          aCloneInstance !== bClone[aCloneIndex] &&
          !equals(aCloneInstance, bClone[aCloneIndex])
        ) {
          loopArrayFlag = false;
        }
      }
    });

    return loopArrayFlag;
  }

  const aRegex = parseRegex(a);
  const bRegex = parseRegex(b);

  if (aRegex[0]) {
    return bRegex[0] ? aRegex[1] === bRegex[1] : false;
  } else if (bRegex[0]) return false;

  const aDate = parseDate(a);
  const bDate = parseDate(b);

  if (aDate[0]) {
    return bDate[0] ? aDate[1] === bDate[1] : false;
  } else if (bDate[0]) return false;

  const aError = parseError(a);
  const bError = parseError(b);

  if (aError[0]) {
    return bError[0]
      ? aError[0] === bError[0] && aError[1] === bError[1]
      : false;
  }

  if (aType === "Object") {
    const aKeys = Object.keys(a);

    if (aKeys.length !== Object.keys(b).length) {
      return false;
    }

    let loopObjectFlag = true;
    aKeys.forEach((aKeyInstance) => {
      if (loopObjectFlag) {
        const aValue = a[aKeyInstance];
        const bValue = b[aKeyInstance];

        if (aValue !== bValue && !equals(aValue, bValue)) {
          loopObjectFlag = false;
        }
      }
    });

    return loopObjectFlag;
  }

  return false;
}

module.exports = equals;

+1 like on the solution of @DLiblik posted above, which also covers dates and functions. Maybe post it in a separate github repository so it can be found more easily?

@edwinro - done - find the gist here: areEquivalent.js

Covers most cases (including the order of the key property if present)

function isEqual(obj1, obj2) {
  function getType(obj) {
    return Object.prototype.toString.call(obj).slice(8, -1).toLowerCase();
  }

  let type = getType(obj1);

  // If the two items are not the same type, return false
  if (type !== getType(obj2)) return false;
  if (type === "array") return areArraysEqual();
  if (type === "object") return areObjectsEqual();
  if (type === "function") return areFunctionsEqual();

  function areArraysEqual() {
    // Check length
    if (obj1.length !== obj2.length) return false;
    // Check each item in the array
    for (let i = 0; i < obj1.length; i++) {
      if (!isEqual(obj1[i], obj2[i])) return false;
    }
    // If no errors, return true
    return true;
  }
  function areObjectsEqual() {
    if (Object.keys(obj1).length !== Object.keys(obj2).length) return false;
    // Check each item in the object
    for (let key in obj1) {
      if (Object.prototype.hasOwnProperty.call(obj1, key)) {
        if (!isEqual(obj1[key], obj2[key])) return false;
      }
    }
    // If no errors, return true
    return true;
  }
  function areFunctionsEqual() {
    return obj1.toString() === obj2.toString();
  }
  function arePrimativesEqual() {
    return obj1 === obj2;
  }
  return arePrimativesEqual();
}