files/en-us/web/api/resizeobserversize/inlinesize/index.md
{{APIRef("Resize Observer API")}}
The inlineSize read-only property of the {{domxref("ResizeObserverSize")}} interface returns the length of the observed element's border box in the inline dimension. For boxes with a horizontal {{cssxref("writing-mode")}}, this is the horizontal dimension, or width; if the writing-mode is vertical, this is the vertical dimension, or height.
[!NOTE] For more explanation of writing modes and block and inline dimensions, read Handling different text directions.
A decimal representing the inline size in pixels.
In this example we return an array of sizing information with {{domxref("ResizeObserverEntry.contentBoxSize")}}. The inlineSize property returns the inline dimension size of the observed element.
const resizeObserver = new ResizeObserver((entries) => {
for (const entry of entries) {
const elemSize = entry.contentBoxSize[0];
console.log(elemSize.inlineSize); // a decimal
}
});
resizeObserver.observe(divElem);
{{Specifications}}
{{Compat}}