jQuery size() Method

What Is size()?

.size() returned the number of elements in a jQuery collection (since 1.0). It was functionally the same as .length, but .length is preferred because it skips a function call. Official docs: deprecated in 1.8, removed in 3.0.

// Legacy (jQuery 1.x / 2.x only):
// $("li").size()

// Modern — use this everywhere:
$("li").length

// Same count, both used to alert "2" for two <li> items
alert("Size: " + $("li").length);

How to Use (Modern: .length)

Select elements, read .length — do not call .size() on jQuery 3+.

1. Build a jQuery collection with a selector or chain.
2. Read .length to get the count as a number.
3. Use that number in conditions, labels, or loops.
4. When migrating, replace .size() with .length (drop the parentheses).

Pseudocode

collection = matched elements

// Legacy:
// n = collection.size()     // function call

// Modern:
n = collection.length        // property read

return n  // integer ≥ 0

// Migration:
// .size()  →  .length

Cheat Sheet

Keep these facts handy when reading or migrating old code.

Live Preview

Count demo items with modern .length (the replacement for .size()).

Ready — pick a count.

jQuery Examples

Runnable demos use modern .length (works on jQuery 3+). Legacy .size() is noted where helpful.

// <ul><li>foo</li><li>bar</li></ul>
// Legacy: $("li").size()
console.log($("li").length);  // 2

2

var n = $("div.box").length;
// Legacy: $("div.box").size()
console.log("There are " + n + " divs.");

There are 3 divs.

console.log($("#missing").length);  // 0
if ($(".modal").length === 0) {
  console.log("No modal on the page");
}

0
No modal on the page

// Before (jQuery 1.x / 2.x):
// var n = $("p").size();

// After (all versions, including 3+):
var n = $("p").length;
console.log(n);

2

console.log(typeof jQuery.fn.size);  // "undefined" on jQuery 3+
console.log($("li").length);         // still works

undefined
2

Performance Notes

Official reason to prefer .length: it avoids a function call. For beginners the bigger win is compatibility with jQuery 3+.

Key Takeaways