svgo-browser/plugins/sortDefsChildren.js

svgo tool for browser and node usage

exports.type = 'perItem';

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).
 *
 * @param {Object} item current iteration item
 * @return {Boolean} if false, item will be filtered out
 *
 * @author David Leston
 */
exports.fn = function (item) {
  if (item.isElem('defs')) {
    if (item.content) {
      const frequency = item.content.reduce((frequency, child) => {
        if (child.elem in frequency) {
          frequency[child.elem]++;
        } else {
          frequency[child.elem] = 1;
        }
        return frequency;
      }, {});
      item.content.sort((a, b) => {
        const frequencyComparison = frequency[b.elem] - frequency[a.elem];
        if (frequencyComparison !== 0) {
          return frequencyComparison;
        }
        const lengthComparison = b.elem.length - a.elem.length;
        if (lengthComparison !== 0) {
          return lengthComparison;
        }
        return a.elem != b.elem ? (a.elem > b.elem ? -1 : 1) : 0;
      });
    }

    return true;
  }
};