strict mode

useStrictMode.md

• this will not refer to window object
• callee, caller of arguments object are not allowed under strict mode
• under strict mode parameter is not refereced linked to arguments object, no strict mode, parameter is a reference of the arguments object.

(function() {
    var nostrict = function(x) {
        arguments[0] = 'modified';
        console.log('arguments[0] =', arguments[0]);
        console.log('x=', arguments[0]);
        console.log('under non-strict mode,', x === arguments[0]); // log true
    };
    var strict = function(x) {
        'use strict';
        arguments[0] = 'modified';
        console.log('arguments[0] =', arguments[0]);
        console.log('x=', arguments[0]);
        console.log('under strict mode', x === arguments[0]); // log false
    };
    nostrict('unmodified');
    strict('unmodified');
})();