espterm-front-end/js/utils.js

/** Make a node */
exports.mk = function mk (e) {
  return document.createElement(e)
}

/** Find one by query */
exports.qs = function qs (s) {
  return document.querySelector(s)
}

/** Find all by query */
exports.qsa = function qsa (s) {
  return document.querySelectorAll(s)
}

/** Convert any to bool safely */
exports.bool = function bool (x) {
  return (x === 1 || x === '1' || x === true || x === 'true')
}

/** Safe json parse */
exports.jsp = function jsp (str) {
  try {
    return JSON.parse(str)
  } catch (e) {
    console.error(e)
    return null
  }
}

/** Decode number from 2B encoding */
exports.parse2B = function parse2B (s, i = 0) {
  return (s.charCodeAt(i++) - 1) + (s.charCodeAt(i) - 1) * 127
}

/** Decode number from 3B encoding */
exports.parse3B = function parse3B (s, i = 0) {
  return (s.charCodeAt(i) - 1) + (s.charCodeAt(i + 1) - 1) * 127 + (s.charCodeAt(i + 2) - 1) * 127 * 127
}

/** Encode using 2B encoding, returns string. */
exports.encode2B = function encode2B (n) {
  let lsb, msb
  lsb = (n % 127)
  n = ((n - lsb) / 127)
  lsb += 1
  msb = (n + 1)
  return String.fromCharCode(lsb) + String.fromCharCode(msb)
}

/** Encode using 3B encoding, returns string. */
exports.encode3B = function encode3B (n) {
  let lsb, msb, xsb
  lsb = (n % 127)
  n = (n - lsb) / 127
  lsb += 1
  msb = (n % 127)
  n = (n - msb) / 127
  msb += 1
  xsb = (n + 1)
  return String.fromCharCode(lsb) + String.fromCharCode(msb) + String.fromCharCode(xsb)
}