Layer Element

Layers were the core of a method of dynamic HTML programming specific to Netscape 4. Each layer was treated as a separate document object in JavaScript. The content could be included in the same file within the non-standard layer element (or any other element with the positioning set to "absolute" via CSS) or loaded from a separate file with or

. It could also be generated via JavaScript with the layer = new Layer constructor. The content would then be inserted into the layer with layer.document.write.

But in modern browsers, the functionality of layers is provided by using an absolutely-positioned div, or, for loading the content from an external file, an IFrame.

Irrelevant to the actual use of layers, when Netscape 4 and Internet Explorer had significantly different JavaScript implementations, a JavaScript program would very often need to run different blocks of code, depending on the browser. To decide which bunches of code to run, a JavaScript program would test for support for layers, regardless of whether the program involved layers at all. Namely,

if( document.layers ) { ...code that would be executed only by Netscape browsers... } else { ...code that would be executed only by Internet Explorer... }

Famous quotes containing the words layer and/or element:

    A revolution is not the overturning of a cart, a reshuffling in the cards of state. It is a process, a swelling, a new growth in the race. If it is real, not simply a trauma, it is another ring in the tree of history, layer upon layer of invisible tissue composing the evidence of a circle.
    Kate Millett (b. 1934)

    Out of the element of participation follows the certainty of faith; out of the element of separation follows the doubt in faith. And each is essential for the nature of faith. Sometimes certainty conquers doubt, but it cannot eliminate doubt. The conquered of today may become the conqueror of tomorrow. Sometimes doubt conquers faith, but it still contains faith. Otherwise it would be indifference.
    Paul Tillich (1886–1965)