Browser support for class syntax in Javascript

Below syntax,

class Polygon {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }
}


var Polygon = class {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }
};



var Polygon = class Polygon {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }
};

--

is supported neither by chrome nor by firefox.

SyntaxError: Unexpected token class(…)

chrome version insalled 47.0.2526.80 m

firefox version installed 44.0a2 (2015-12-12)

Which version of browser does class & extends keywords gets supported?

1. You can use a javascript to javascript compiler such as Babel to compile ES6 javascript into ES5 code. It covers most of the ES6 features.

2. Take a look at https://kangax.github.io/compat-table/es6/ for a table of ES6 features and how well are they supported by different browsers.