What's the difference between Javascript Object and JSON object

Question

Can anyone tell me the difference between Javascript Object and JSON object with an example?

Answer 1

JSON is a text representation of a javscript object. It is effectively an object literal in javascript notation (hence the name - JavaScript Object Notation => JSON).

If you want to "compare" two object, convert the text to objects then compare keys and values.

Some examples of objects to/from text:

// Create obj using an object literal
var obj = {key: 'value'};

// Convert to text using JSON.stringify
var text = JSON.stringify(obj);

// Show the value of text
alert( text ); // {"key":"value"}

// Create a new object from text
var newObj = JSON.parse(text); // javascript object

// Show the text version of newObj
alert(JSON.stringify(newObj));  // {"key":"value"}

// Use text as code
var newObj2 = eval('(' + text + ')');

// It is indeed a string literal
alert(JSON.stringify(newObj2));  // {"key":"value"}

If you want to compare two objects, convert them from JSON to objects (if they are JSON in the first place) then do something like:

function compareObjects(a, b) {
  var i, p, aProps = [], bProps = [];

  // Simple test first
  if (a === b) {
    return true;
  }

  // Get properties of a
  for (p in a) {
    if (a.hasOwnProperty(p)) {
      aProps.push(p);
    } 
  }

  // Get properties of b
  for (p in b ) {
    if (b.hasOwnProperty(p)) {
      bProps.push(p);
    } 
  }

  // If don't have same properties, return false
  if (aProps.sort().join('') != bProps.sort().join('')) {
    return false;
  }

  // If property values aren't the same, return false
  i = aProps.length;
  while (i--) {
    if (a[aProps[i]] !== b[bProps[i]]) {
      return false;
    }
  }

  // If passed all tests, must be equal
  return true;
}