getElementById

getElementById is a method of the Document interface in the Document Object Model (DOM). It returns a reference to the element whose id attribute matches the provided string, or null if no such element exists. The id value is expected to be unique within a document.

Usage is straightforward: var el = document.getElementById('myId'); if (el) { el.textContent = 'Hello'; } This pattern is common for accessing a specific element to read or modify its properties or content.

Notes and behavior: getElementById searches the current document for an element with the given id. Because IDs are intended to be unique, the method returns at most one element. The result is a direct reference to the element in the DOM; if the element is removed or its id is changed after retrieval, subsequent DOM operations may reflect that change.

Compatibility and alternatives: The method is supported by all major browsers. For more flexible selection, developers may use querySelector('#myId'), which accepts CSS selectors but can be slower in tight loops. getElementById remains a fast and reliable way to access a single element by its id.

See also: querySelector, getElementsByTagName.