If you are using var ALWAYS declare your variables at the top. So you can use a variable before it has been declared. It is availble in the whole function even before being declared. Return x // gets redefined because line 4 declaration is hoistedįor test(false) you would expect to return outer, BUT NO, you get undefined.īecause even though the if-block is not executed, the expression var x in line 4 is hoisted. The issue with var is the variable leaks into other code block such as for loops or if blocks. With ES6, we went from declaring variables with var to use let/ const. So don’t take my word and test every ES5 and ES6 example. You can test all these code snippets on your browser console! Let’s get started with ECMAScript 6! Core ES6 Features So, everything that you are going to learn in this tutorial you can start using it right now. Browsers SupportĪll modern browser and environments support ES6 already!Ĭhrome, MS Edge, Firefox, Safari, Node and many others have already built-in support for most of the features of JavaScript ES6. Instead of doing massive changes at once like happened with ES6. The new model is to make small incremental changes every year.

It has been releasing versions such as ES3, ES5, ES6 and so on.Īs you can see, there are gaps of 10 and 6 years between the ES3, ES5, and ES6. ECMAScript came to be in 1997 to guide the path of JavaScript. Since JavaScript conception on 1995, it has been evolving slowly. The new additions to the language are called ECMAScript 6. These are 12 new features that you can start using today! JavaScript History JavaScript has changed quite a bit in the last years.

Ecmascript 6