The selectors point to the HTML element you want to set the style. The selector is the technic to give any kind of style to your text on your HTML page.
Javascript toggle method simply toggles the visibility of elements. The matched elements will be revealed or hidden immediately, with no animation, by changing the CSS display property.
QR code (Quick Response Code) is the trademark for a type of matrix barcode. A QR code is a machine-readable code consisting of an array of black and white squares.
