Thursday, December 20, 2012

Native JSON parsing

Starting from Internet Explorer 8+, Firefox 3.1+, Safari 4+, Chrome 3+, and Opera 10.5+ browsers support native JSON parsing. But what if your users are still using IE7 (or even worse IE6)?

Here are some of the options I prefer to use:

  • To convert a JSON response to a JavaScript object:
    • If you are using jQuery, use parseJSON. Internally it checks if browser supports JSON.parse, so the fallback is built in.
    • Use the JSON.parse method from the json2.js library from Douglas Crockford. It adds a JSON object to the browser if it doesn’t exists yet.
  • To convert a JavaScript object to serialized JSON string:
    • For jQuery I couldn’t find an out-of-the-box solution, but the following jQuery plugin could do the trick: jQuery.toJSON
    • Use the JSON.stringify method from the json2.js library.

What I also like about the json2.js library from Douglas Crockford is that it allows you to manipulate the serialization process by adding a toJSON method to your JavaScript objects.

When an object value is found, if the object contains a toJSON method, its toJSON method will be called and the result will be stringified. A toJSON method does not serialize: it returns the value represented by the name/value pair that should be serialized, or undefined if nothing should be serialized. The toJSON method will be passed the key associated with the value, and this will be bound to the value

For example, this would serialize Dates as ISO strings:

Date.prototype.toJSON = function (key) {
function f(n) {
// Format integers to have at least two digits.
return n < 10 ? '0' + n : n;

return this.getUTCFullYear() + '-' +
f(this.getUTCMonth() + 1) + '-' +
f(this.getUTCDate()) + 'T' +
f(this.getUTCHours()) + ':' +
f(this.getUTCMinutes()) + ':' +
f(this.getUTCSeconds()) + 'Z';

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