In one sentence, ECMAScript for the JavaScript developer is like the Java Specification for the Java Developer.

 

Ecma_java

 

In your development you have to decide which version of ECMAScript target, we suggest that you monitor the ECMA implementation status with websites like http://kangax.github.io/compat-table/es5/

Each Runtime environment can have a different level of implementation of the features of a defined specification.

At the time of writing this post ECMAScript 2015 is the ‘standard’ for the web browser e.g.:

Ecma_compatibility_table

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Remember: In JavaScript you can develop using an ECMAScript version different to the ECMAScript version of the target.

To convert your code you need a Transpiler. We will write an article about it.