ECMAScript first 5 versions
1. strict mode :
What is : than ordinary js operational mechanism to require more stringent mode
Why : js language itself has many flaws widely criticized
When : all future js procedures must be run in strict mode!
How to :
At the top of the current scope write : "use strict"; - Enable strict mode
Provisions :
1. Prohibition to undeclared variable assignment :
2. fail silently upgrade error :
What is silent failures : Unsuccessful, but not an error.
ES5 specified , all silent failure , have been upgraded for the error !
3. anonymous function from an ordinary function call to reconcile the this , no longer points to window ! But the this = undefined .