vue hello world项目
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'use strict';
exports.type = 'visitor';
exports.name = 'sortDefsChildren';
exports.active = true;
exports.description = 'Sorts children of <defs> to improve compression';
/**
* Sorts children of defs in order to improve compression.
* Sorted first by frequency then by element name length then by element name (to ensure grouping).
*
* @author David Leston
*
* @type {import('../lib/types').Plugin<void>}
*/
exports.fn = () => {
return {
element: {
enter: (node) => {
if (node.name === 'defs') {
/**
* @type {Map<string, number>}
*/
const frequencies = new Map();
for (const child of node.children) {
if (child.type === 'element') {
const frequency = frequencies.get(child.name);
if (frequency == null) {
frequencies.set(child.name, 1);
} else {
frequencies.set(child.name, frequency + 1);
}
}
}
node.children.sort((a, b) => {
if (a.type !== 'element' || b.type !== 'element') {
return 0;
}
const aFrequency = frequencies.get(a.name);
const bFrequency = frequencies.get(b.name);
if (aFrequency != null && bFrequency != null) {
const frequencyComparison = bFrequency - aFrequency;
if (frequencyComparison !== 0) {
return frequencyComparison;
}
}
const lengthComparison = b.name.length - a.name.length;
if (lengthComparison !== 0) {
return lengthComparison;
}
if (a.name !== b.name) {
return a.name > b.name ? -1 : 1;
}
return 0;
});
}
},
},
};
};