Javascript performance. Array vs Object.

Big JavaScript application needs big storage. JS gives us 2 options Array and Object. I have tested following cases:

• writing data
• writing data randomly
• reading data
• reading data randomly

I have tested this in following browsers:

• IE
• FF
• Chrome

I want to point out that i am not comparing browsers. I am comparing two methods of storing data in JavaScript.

I have checked perfomance of following pices of code:

writing [ ]

// initialization
var r=[];
//code to evaluate
for (i=0;i<10000;i++){
    this.r[i]=7;
}

writing {}

// initialization
var r={};
//code to evaluate
for (i=0;i<10000;i++){
    this.r[i]=7;
}

writing [ ] randomly

// initialization
var r=[];
//code to evaluate
for (i=0;i<10000;i++){
    this.r[Math.floor(Math.random(1000))]=7;
}

writing { } randomly

// initialization
var r={};
//code to evaluate
for (i=0;i<10000;i++){
    this.r[Math.floor(Math.random(1000))]=7;
}

Here are results in ms:

Ok the result shows us that the perfomance of Array and Object as storage is almost equal.
So semantically i think it is wise to use array for unordered information and object for mapping.