| ES5 is the 5th edition of ECMAScript which was STANDARDIZED in 2009. This version has been successfully implemented in all web browsers. | ES6 is the 6TH edition of ECMAScript which was standardized in 2015. This version has been partially implemented in most web browsers. |
| The function keyword is MANDATORY to use to define the functions. | In this, to define the function, the function keyword is not needed. |
| The return keyword is also mandatory to use to define the functions | The return keyword is not needed to define the functions. |
| ES5 has lower performance due to the absence of a few features. | ES6 has a COMPARATIVELY higher performance. |
