Literal object and function constructor

问题

I took this test on http://jsperf.com/literal-obj-vs-function-obj and Literal wins on FF6, Opera 10, IE8, but the Function method faster on Chrome 13.0.782.112, so which one is a better method to use?

var A = {
    aa : function(){
        var i, j=[];
        var arr = ['Literal', 'Function'];
        for (i = 0; i < arr.length; i++){
            j[i] = arr[i];
        }
       return j[0];
    }
};
var A1 = A;
var A2 = A1;
A1.foo = ' Test';
alert(A1.aa() + A2.foo);

//Function test
function B(){
    this.bb = function(){
        var i, j=[];
        var arr = ['Literal', 'Function'];
        for (i = 0; i < arr.length; i++){
            j[i] = arr[i];
        }
        return j[1];
    }
}
var B1 = new B();
var B2 = new B();
B.prototype.foo = ' Test';
alert(B1.bb() + B2.foo);

回答1:

To tell you the truth, the best that I have found is a mix:

function C() {
    var i, j = [],
        foo;

    return {
        bb: function() {

            var arr = ['Literal', 'Function'];
            for (i = 0; i < arr.length; i++) {
                j[i] = arr[i];
            }
            return j[1];
        },
        setFoo: function(val) {
            foo = val;
        },
        getFoo: function() {
            return foo;
        }
    }
}
var C1 = C();
var C2 = C();
C2.setFoo(' Test');
console.log(C1.bb(), C2.getFoo());

回答2:

Whichever one you prefer. Speed should never be a concern unless it becomes a real problem in your app. What you're doing looks like premature optimization to me, which is a waste of time. Wait until you need to optimize your code, then optimize the parts that need to be reworked. This is trivial.

回答3:

Chrome uses an optimisation called hidden classes that allows it to do faster access to object members.

I would bet that this optimisation is enabled only when the object is constructed via new, and as a result an object constructed via new would have faster member access than an object not constructed via new.

回答4:

well, chrome has around 17% of the market share according to wikipedia. So use literals.

回答5:

I doubt you're going to do anything intensive enough for the difference to matter.

Function style constructors give you the option of private variables, which is nice.

来源：https://stackoverflow.com/questions/7152005/literal-object-and-function-constructor