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// Some really simple functions for formatting HTML content.
// COMPREHENSIVE!
// https://html.spec.whatwg.org/multipage/syntax.html#void-elements
export const selfClosingTags = [
'area',
'base',
'br',
'col',
'embed',
'hr',
'img',
'input',
'link',
'meta',
'source',
'track',
'wbr',
];
// Pass to tag() as an attributes key to make tag() return a 8lank string if the
// provided content is empty. Useful for when you'll only 8e showing an element
// according to the presence of content that would 8elong there.
export const onlyIfContent = Symbol();
// Pass to tag() as an attributes key to make children be joined together by the
// provided string. This is handy, for example, for joining lines by <br> tags,
// or putting some other divider between each child. Note this will only have an
// effect if the tag content is passed as an array of children and not a single
// string.
export const joinChildren = Symbol();
// Pass to tag() as an attributes key to prevent additional whitespace from
// being added to the inner start and end of the tag's content - basically,
// ensuring that the start of the content begins immediately after the ">"
// ending the opening tag, and ends immediately before the "<" at the start of
// the closing tag. This has effect when a single child spans multiple lines,
// or when there are multiple children.
export const noEdgeWhitespace = Symbol();
export function tag(tagName, ...args) {
const selfClosing = selfClosingTags.includes(tagName);
let openTag;
let content;
let attrs;
if (typeof args[0] === 'object' && !Array.isArray(args[0])) {
attrs = args[0];
content = args[1];
} else {
content = args[0];
}
if (selfClosing && content) {
throw new Error(`Tag <${tagName}> is self-closing but got content!`);
}
if (attrs?.[onlyIfContent] && !content) {
return '';
}
if (attrs) {
const attrString = attributes(attrs);
if (attrString) {
openTag = `${tagName} ${attrString}`;
}
}
if (!openTag) {
openTag = tagName;
}
if (Array.isArray(content)) {
if (content.some(item => Array.isArray(item))) {
throw new Error(`Found array instead of string (tag) or null/falsey, did you forget to \`...\` spread an array or fragment?`);
}
const joiner = attrs?.[joinChildren];
content = content.filter(Boolean).join(
(joiner
? `\n${joiner}\n`
: '\n'));
}
if (content) {
if (content.includes('\n')) {
return [
`<${openTag}>`,
content
.split('\n')
.map((line, i) =>
(i === 0 && attrs?.[noEdgeWhitespace]
? line
: ' ' + line))
.join('\n'),
`</${tagName}>`,
].join(
(attrs?.[noEdgeWhitespace]
? ''
: '\n'));
} else {
return `<${openTag}>${content}</${tagName}>`;
}
} else {
if (selfClosing) {
return `<${openTag}>`;
} else {
return `<${openTag}></${tagName}>`;
}
}
}
export function escapeAttributeValue(value) {
return value.replaceAll('"', '"').replaceAll("'", ''');
}
export function attributes(attribs) {
return Object.entries(attribs)
.map(([key, val]) => {
if (typeof val === 'undefined' || val === null)
return [key, val, false];
else if (typeof val === 'string')
return [key, val, true];
else if (typeof val === 'boolean')
return [key, val, val];
else if (typeof val === 'number')
return [key, val.toString(), true];
else if (Array.isArray(val))
return [key, val.filter(Boolean).join(' '), val.length > 0];
else
throw new Error(`Attribute value for ${key} should be primitive or array, got ${typeof val}`);
})
.filter(([_key, _val, keep]) => keep)
.map(([key, val]) =>
typeof val === 'boolean'
? `${key}`
: `${key}="${escapeAttributeValue(val)}"`
)
.join(' ');
}
// Ensures the passed value is an array of elements, for usage in [...spread]
// syntax. This may be used when it's not guaranteed whether the return value of
// an external function is one child or an array, or in combination with
// conditionals, e.g. fragment(cond && [x, y, z]).
export function fragment(childOrChildren) {
if (!childOrChildren) {
return [];
}
if (Array.isArray(childOrChildren)) {
return childOrChildren;
}
return [childOrChildren];
}
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