selectionStart

selectionStart is a numeric property of text input and textarea elements in the HTML DOM. It indicates the position, in characters, of the start of the current text selection within the element’s value, counted from 0 at the beginning.

If there is no selection, the value of selectionStart corresponds to the caret’s position. The property is typically read/write, allowing scripts to read the caret location or move it by assigning a new value. It is commonly used together with selectionEnd to determine or modify the selected range, or with the method setSelectionRange to select text programmatically.

Scope and compatibility: selectionStart applies to input elements of type text and related text inputs as well as textareas. It is not defined for most contenteditable elements, which are handled via the Selection and Range APIs. In older browsers such as pre-IE9, non-standard approaches were used.

Example: var start = input.selectionStart; var end = input.selectionEnd; input.setSelectionRange(5, 10);