Javascript 5 introduced the concept of strict mode.
Strict mode is a different parsing and execution model for JavaScript, where some of the erratic behavior is addressed.
To enable strict mode for an entire script, include the following at the top:
"use strict";
This is a pragma that tells supporting JavaScript engines to change into strict mode.
You may specify a function to execute in strict mode by including the pragma at the top of the function body:
function doSomething(){
"use strict";
//function body
}
When you are running in strict mode, you cannot define variables
named eval or arguments. Doing so results in a syntax error.
Both eval and arguments are reserved words.