This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The size read-only property of the StylePropertyMapReadOnly interface returns an unsinged long integer containing the size of the StylePropertyMapReadOnly object.


var size = StylePropertyMapReadOnly.size


An unsigned long integer.


Here we use the size property to return the total entries within the button elements computedStyleMap.

// grab our element
const buttonEl = document.querySelector('button');

// we can retrieve all computed styles with `computedStyleMap`
const allComputedStyles = buttonEl.computedStyleMap();

// use size to get the total styles within the map
const amountStyles = allComputedStyles.size;
console.log(amountStyles); // logs 338


Specification Status Comment
CSS Typed OM Level 1
The definition of 'size' in that specification.
Working Draft Initial definition.

Browser compatibility

BCD tables only load in the browser