# Pattern

## What is it

## When to use it

## How to use it

The tabbed user interface enables users to jump to their target section quickly. Tabs present like logically group information on the same page. Information should

- be logically chunked and ordered
- be arallel in nature
- show user's context
- obvious where they begin and end

Users should not need to see content of multiple tabs simultaneously and the user should be able to easily recognise where they are within the content.

The tab module can be initialised by importing a file with the javascript module using import * as tabs from "../pg/patterns/layouts/tabs/_tabs.js"; contains a modularized version of the jQuery code, so that it can be called on demand. It is what is used in the design system so that the JavaScript can be called at run time (after loading content).

    tabset, .tab-group {
    	margin: 2rem 0 1rem 0;
    }
    tabset > ul, .tab-group > ul {
    	display: -webkit-box;
    	display: -ms-flexbox;
    	display: flex;
    	margin: 0;
    	padding: 0;
    }
    tabset > ul li.separator, .tab-group > ul li.separator {
    	border-bottom: 1px solid var(--colour-grey);
    	border-left: 1px solid var(--colour-grey);
    	display: inline-block;
    	margin: 0.45rem 0 0 0;
    	width: 100%;
    }
    tabset .tab-hidden, .tab-group .tab-hidden {
    	display: none;
    }
    tabset [role=tab], .tab-group [role=tab] {
    	background-color: var(--colour-white);
    	border-left: 1px solid var(--colour-grey);
    	border-top: 1px solid var(--colour-grey);
    	border-radius: 0.5rem 0.5rem 0 0;
    	cursor: pointer;
    	margin: 0;
    	display: inline;
    	padding: 1rem 1.5rem 0.14rem 1.5rem;
    	z-index: 2;
    }
    tabset [role=tab]:last-of-type, .tab-group [role=tab]:last-of-type {
    	border-right: 1px solid var(--colour-grey);
    }
    tabset [role=tab]:not(.selected), .tab-group [role=tab]:not(.selected) {
    	background-color: var(--colour-grey-xxl);
    	border-bottom: 1px solid var(--colour-grey);
    }
    tabset [role=tab] span, .tab-group [role=tab] span {
    	display: block;
    	margin: 0 0 0.5rem 0;
    }
    tabset [role=tabpanel], .tab-group [role=tabpanel] {
    	background-color: var(--colour-white);
    	border: 1px solid var(--colour-grey);
    	border-top: none;
    	padding: 1rem;
    	z-index: 1;
    }
    tabset [role=tabpanel]:not(.open), .tab-group [role=tabpanel]:not(.open) {
    	display: none;
    }

    //		DS2 core (c) 2024 Alexander McIlwraith
    //		Licensed under CC BY-SA 4.0

    $tab-border: var(--colour-grey) !default;
    $tab-selected: var(--colour-white) !default;
    $tab-notselected: var(--colour-grey-xxl) !default;

    @mixin tabs {
    	tabset, .tab-group {
    		margin: 2rem 0 1rem 0;
    		> ul {
    			display: flex;
    			margin: 0;
    			padding: 0;

    			li.separator {
    				border-bottom: 1px solid $tab-border;
    				border-left: 1px solid $tab-border;
    				display: inline-block;
    				margin: .45rem 0 0 0;
    				width: 100%;
    			}
    		}

    		.tab-hidden {
    			display: none;
    		}

    		[role="tab"] {
    			background-color: $tab-selected;
    			border-left: 1px solid $tab-border;
    			border-top: 1px solid $tab-border;
    			border-radius: .5rem .5rem 0 0;
    			cursor:pointer;
    			margin: 0;
    			display: inline;
    			padding: 1rem 1.5rem .14rem 1.5rem;
    			z-index: 2;

    			&:last-of-type {
    				border-right: 1px solid $tab-border;
    			}

    			&:not(.selected) {
    				background-color: $tab-notselected;
    				border-bottom: 1px solid $tab-border;
    			}

    			span {
    				display: block;
    				margin: 0 0 .5rem 0;
    			}

    		}
    		[role="tabpanel"] {
    			background-color: $tab-selected;
    			border: 1px solid $tab-border;
    			border-top: none;
    			padding: 1rem;
    			z-index: 1;

    			&:not(.open) {
    				display: none;
    			}
    			@content;

    		}
    	}
    }

    /*  DS2 core (c) 2024 Alexander McIlwraith
    	import * as tabs from "../pg/patterns/layouts/tabs/_tabs.js";
    	tabs.init();
     */

    export function init(p = document) {
    	p.querySelectorAll(".tab-group, tabset").forEach(tabGroup => {

    		if (tabGroup.querySelector("[role=tablist]") === null) {
    			const tabgroup = tabGroup.getAttribute("id");
    			let tablist = "";

    			Array.from(tabGroup.children).forEach(child => {
    				const tab = child.getAttribute("tab") || child.getAttribute("data-tab");
    				if (tab !== null) {
    					const tabID = tab.replace(/\W+/g, "-").toLowerCase();
    					const tabPanel = document.createElement('div');
    					tabPanel.id = `tab-panel-${tabgroup}-${tabID}`;
    					tabPanel.className = tablist === "" ? "open" : "";
    					tabPanel.setAttribute("role", "tabpanel");
    					tabPanel.setAttribute("tabindex", "0");
    					tabPanel.setAttribute("aria-labelledby", `tab-${tabgroup}-${tabID}`);
    					tabPanel.appendChild(child.cloneNode(true));
    					child.parentNode.replaceChild(tabPanel, child);
    					tablist += `${tab}`;
    				} else {
    					child.classList.add("tab-hidden");
    				}
    			});

    			const ul = document.createElement('ul');
    			ul.setAttribute("role", "tablist");
    			ul.innerHTML = `${tablist}`;
    			tabGroup.insertBefore(ul, tabGroup.firstChild);

    			tabGroup.querySelectorAll('[role="tab"]').forEach(tab => {
    				tab.addEventListener("click", () => {
    					const siblings = Array.from(tab.parentNode.children);
    					siblings.forEach(sibling => sibling.classList.remove("selected"));
    					tab.classList.add("selected");

    					const tabPanels = Array.from(tab.parentNode.parentNode.children)
    										   .filter(child => child.getAttribute("role") === "tabpanel");
    					tabPanels.forEach(panel => panel.classList.remove("open"));

    					const tabPanelId = tab.getAttribute("id").replace("tab", "tab-panel");
    					document.getElementById(tabPanelId).classList.add("open");
    				});
    			});

    		}
    	});
    }