Wie 'new' und 'strict mode' zusammenhängen.

gistfile1.js

console.clear();

/*
In both functions below, MyObj has the same declaration, but if they're called as strict or non-strict depends on the place where it's defined.
*/

(function() {
    console.log("Without strict mode:");
    
    var MyObj = function (name) {
        console.log("myScope for ", name, ":", this);
    };
        
    /* 
    This will print 'Unstrict: {top, window, location, ...}'
    because no new Scope is created for the constructor. 
    Instead, the current scope is the document here.
    Variable declarations in constructor will create
    global variables.
    */
    MyObj("Unstrict");
    
    /*
    This will print 'Unstrict with new: MyObj {}' 
    because a new Scope is created with the new keyword. 
    Actions in contructor won't modify the global scope.
    */
    new MyObj("Unstrict with new");
})();

(function() {
    "use strict";
    console.log("With strict mode:");
    
    var MyObj = function (name) {
        console.log("myScope for ", name, ":", this);
    };

    /* 
    This will print 'Strict: undefined'
    because no new Scope is created for the constructor and
    it would ne unsafe to pass in the global object.
    */
    MyObj("Strict");
    
    /*
    In strict mode, this is the only correct way to create a
    new object. It will print 'Strict with new: MyObj {}'.
    */
    new MyObj("Strict with new");
})();