CSS.escape shim function that works in browser & node.

css_escape_shim.js

/**
 * CSS escape shim that works in both node and the browser.
 *
 * see: https://github.com/mathiasbynens/CSS.escape/blob/master/css.escape.js
*/
export function escape(sel) {
  const result = [];

  for (const [index, letter] of Array.from(sel).entries()) {
    const charCode = letter.charCodeAt(0);

    if (charCode === 0x0000) {
      result.push('\uFFFD');

      continue;
    }

    if (
      (charCode >= 0x0001 && charCode <= 0x001F)
      || charCode === 0x007F
      || (index === 0 && charCode >= 0x0030 && charCode <= 0x0039)
      || (
          index === 1
          && charCode >= 0x0030
          && charCode <= 0x0039
          && sel.charCodeAt(0) === 0x002D
        )
    ) {
      result.push(`\\${charCode.toString(16)} `);

      continue;
    }

    if (
      charCode >= 0x0080
      || charCode === 0x002D
      || charCode === 0x005F
      || (charCode >= 0x0030 && charCode <= 0x0039)
      || (charCode >= 0x0041 && charCode <= 0x005A)
      || (charCode >= 0x0061 && charCode <= 0x007A)
    ) {
      result.push(letter);

      continue;
    }

    result.push(`\\${letter}`);
  }

  return result.join('');
}

export default {
  escape,
};