QIE uses the Mozilla Rhino based JavaScript engine that is included with the Java runtime. The JavaScript version that is supported depends on which version of the Rhino engine is being used.
Java 6 supports the 1.6R2 Rhino version which supports JavaScript 1.5.
Java 7 supports the 1.7R3 Rhino version which supports JavaScript 1.8.
The Oracle versions of Java include a slightly modified version of the Rhino engine. Details for what has been excluded can be found
here for Java 6 and
here for Java 7.
ECMAScript is the specification that the JavaScript language is based upon. The ECMAScript edition that is supported depends on which version of JavaScript is supported.
JavaScript 1.5 & 1.7 support ECMAScript 3rd edition.
JavaScript 1.8 supports ECMAScript 5th edition.
More information about EMCAScript can be found
here.