4.4 Deep Comparison (Eloquent JavaScript Solutions)

4-4 Eloquent Javascript Solutions.js

function deepEqual(a, b) {
  if (a === b) {
    // items are identical
    return true;
  } else if (typeof a === 'object' && a !== null && typeof b === 'object' && b !== null) {
  	// items are objects - do a deep property value compare
    // join keys from both objects together in one array
    let keys = Object.keys(a).concat(Object.keys(b));
    // filter out duplicate keys
    keys = keys.filter(
      function (value, index, self) { 
        return self.indexOf(value) === index;
	  }
    );
    for (p of keys) {
      if (typeof a[p] === 'object' && typeof b[p] === 'object') {
        if (deepEqual(a[p], b[p]) === false) {
          return false;
        }
      } else if (a[p] !== b[p]) {
        return false;
      }
    }
    return true;
  } else {
   return false; 
  }
}

// Tests

let obj = {here: {is: "an"}, object: 2};
console.log(deepEqual(obj, obj));
// → true
console.log(deepEqual(obj, {here: 1, object: 2}));
// → false
console.log(deepEqual(obj, {here: {is: "an"}, object: 2}));
// → true
console.log(deepEqual(obj, {here: {is: "an"}, object: 0}));
// → false
console.log(deepEqual(obj, {here: {is: "another"}, object: 2}));
// → false
console.log(deepEqual(obj, {here: {isnt: "an"}, object: 2}));
// → false
console.log(deepEqual(obj, {here: {is: "an", deep: {poop: null, value: -1}}, object: 2}));
// → false
let json = '{"candidate": "Jon Urry", "job": "Junior Full-Stack JavaScript Developer", "portfolio": "jon.urry.me", "skills": ["HTML", "CSS", "JavaScript", "ES6", "Node", "React", "Vue", "Git", "XML", "UX", "Responsive Design", "Design Patterns", "TDD", "Chrome Inspector", "Agile", "SEO", "Analytics", "WordPress", "Databases"], "contact": [{"email": "mailto:jon@urry.me"}, {"github": "github.com/jonurry"}, {"linkedin": "linkedin.com/in/jonurry"}, {"mobile": "tel:+44-7986-371-299"}, {"skype": "skype:jonurry"}, {"twitter": "twitter.com/jonurry"}]}';
let json2 = '{"candidate": "Jon Urry", "job": "Junior Full-Stack JavaScript Developer", "portfolio": "jon.urry.me", "skills": ["HTML", "CSS", "JavaScript", "ES6", "Node", "React", "Vue", "Git", "XML", "UX", "Responsive Design", "Design Patterns", "TDD", "Chrome Inspector", "Agile", "SEO", "Analytics", "WordPress", "Databases2"], "contact": [{"email": "mailto:jon@urry.me"}, {"github": "github.com/jonurry"}, {"linkedin": "linkedin.com/in/jonurry"}, {"mobile": "tel:+44-7986-371-299"}, {"skype": "skype:jonurry"}, {"twitter2": "twitter.com/jonurry2"}]}';
let jsonObj = JSON.parse(json);
let jsonObjCopy = JSON.parse(JSON.stringify(jsonObj));
let jsonObj2 = JSON.parse(json2);
console.log(jsonObj);
console.log(deepEqual(jsonObj, jsonObj));
// → true
console.log(deepEqual(jsonObj, jsonObjCopy));
// → true
console.log(deepEqual(jsonObj, jsonObj2));
// → false
console.log(deepEqual(null, obj));
// → false
console.log(deepEqual(obj, null));
// → false
console.log(deepEqual(null, null));
// → true

Hi I came up with the following solution but it is not working for second and third tests as expected, any insights would be appreciated:

// Your code here.
function deepEqual(val1, val2){

if ((val1 != null && typeof val1 == "object") && (val2 != null && typeof val2 == "object")){

if(Object.keys(val1).length != Object.keys(val2).length){
  return false;
} else {
  for (let props of Object.keys(val1)){
    
  	if(!Object.keys(val2).includes(props)){
      return false;
      break;
    } 
    
    if(val2[props] != val1[props]){
      return false;
      break;
    }; 
    
  };
  return true;
};    

} else {
return val1 === val2;
};
};

let obj = {here: {is: "an"}, object: 2};

console.log(deepEqual(obj, obj));
// → true
//console.log(deepEqual(obj, {here: 1, object: 2}));
// → false
console.log(deepEqual(obj, {here: {is: "an"}, object: 2}));
// → true

if (a === b) {
    // items are identical
    return true;
  }

you can add this line

if (a === b) {
    // items are identical
    return true && Object.is(a,b);
  }

in this way it will not evaluate as true the following expression:

deepEqual(+0, -0); // true

Hey, I found a bug in the code.

deepEqual({here: "is", here: "is"}, {here: "is"})
// returns true

I know this comment has a couple years on it, but ....
You can't have a hash with two like key values I'm pretty sure. And knowing JavaScript being all floppy, it doesn't complain about it, it just overwrite's the previously assigned values to that key.