The selectionStart property of the HTMLInputElement interface is a number that represents the beginning index of the selected text. When nothing is selected, it returns the position of the text input cursor (caret) inside of the <input> element.
Note: According to the WHATWG forms spec, the selectionStart property applies only to inputs of types text, search, URL, tel, and password. On other input types, reading selectionStart returns null, and setting it throws an InvalidStateError.
If selectionStart is greater than selectionEnd, then both are treated as the value of selectionEnd.
A non-negative number.
<!-- use selectionStart on non text input element -->
<label for="color">selectionStart property on type=color</label>
<input id="color" type="color" />
<!-- use selectionStart on text input element -->
<fieldset>
<legend>selectionStart property on type=text</legend>
<label for="statement">Select 'mdn' word from the text : </label>
<input
type="text"
id="statement"
value="The mdn is a documentation repository." />
<button id="statement-btn">Select mdn text</button>
</fieldset>const inputElement = document.getElementById("statement");
const statementBtn = document.getElementById("statement-btn");
const colorStart = document.getElementById("color");
statementBtn.addEventListener("click", () => {
inputElement.selectionStart = 4;
inputElement.selectionEnd = 7;
inputElement.focus();
});
// open browser console to verify output
console.log(colorStart.selectionStart); // Output : nullHTMLTextAreaElement.selectionStart propertyHTMLInputElement.selectionEnd propertyHTMLInputElement.setSelectionRange method