performance « variable « Javascript Data Type Q&A

1. Declaring Multiple Variables in JavaScript    stackoverflow.com

In JavaScript, it is possible to declare multiple variables like this:

var variable1 = "Hello World!";
var variable2 = "Testing...";
var variable3 = 42;

var variable1 = "Hello World!",
    variable2 ...

2. JS 1-2k variables make page load slow    stackoverflow.com

On one page of my website the user has the ability to choose and remove up to 2000 items through selecting multiple string representations of them in a dropdown list. On ...

3. Should I cache document.getElementById() in a variable or call it everytime?    stackoverflow.com

I'm having a lot of elements which are generated and referenced (mouseover, clicks, position changes) a lot of times. I have the ID's of those elements at hand. Is it wise to ...

4. Does this javascript statement affects performance?    stackoverflow.com

I'm writing a function add_event as the following shows:

function add_event(o, event_type, callback, capture){
    o = typeof o === "string" ? document.getElementById(o) : o;
    if(document.addEventListener){
  ...

5. How expensive are variables in JavaScript?    stackoverflow.com

How expensive are local variables (var v), global variables (window.v) and cross-global variables (parent.v) in JavaScript, in the major browsers? Has anyone performed any good tests on this one?

6. what's more efficient? checking == or just mutating the variable?    stackoverflow.com

Imagine I had a variable called X. Let's say every 5 seconds I wanted to make X = true. (it could be either true or false in between these 5 seconds, but ...

7. Local variable vs parameter    stackoverflow.com

function doIt(param) {
   var localVar = param;
   //do lots of stuff with localVar
}

function doIt(param) {
   //do lots of stuff with param
}

8. Is there a performance hit of replacing local variables with arguments in Javascript?    stackoverflow.com

Is there any performance hit for writing a function such that local var statements are replaced with arguments? Example:

function howManyMatch(arr, pattern, /*ignored:*/ i, l, total) {
  l = arr.length;
  ...

9. testing js variable declaration speed    stackoverflow.com

I want to do some speed tests on very basic stuff like variable declaration. Now i have a function that executes X times to have a more significant time difference. http://jsfiddle.net/eTbsv/ ...

10. Javascript clears a variable after there is no further reference it    stackoverflow.com

It is said, javascript clears a variable from memory after its being referenced last. just for the sake of this question i created a JS file for DEMO with only one ...

11. Javascript toLowerCase() performance versus variable creation    stackoverflow.com

What is more efficient?:

var text="ABCdef";
var lowerVersion=text.toLowerCase();
if (lowerVersion=='abcdef' || lowerVersion=='asdfgh' || lowerVersion=='zxcvbn'){...

var text="ABCdef";
if (text.toLowerCase()=='abcdef' || text.toLowerCase()=='asdfgh' || text.toLowerCase()=='zxcvbn'){...