oo-logger-base.html

<script>
  // Declare in local function scope to avoid bleeding variables into global `window`.
  (function () {

    // Declare or reuse global namespace.
    window.oo = window.oo || {}

    oo.buildLog = function buildLog(context, level, timestamp, ...messages) {
      _checkNotNil(context, () => "illegal argument: context is missing")
      _checkNotNil(level, () => "illegal argument: level is missing")
      _checkNotNil(timestamp, () => "illegal argument: timestamp is missing")

      const timestampStr = _formatDate(timestamp)
      const levelStr = _padLeft("|" + level + "|", 7, " ")
      const contextStr = "[" + context + "]"

      return [timestampStr, levelStr, contextStr, ...messages]
    }

    function _formatDate(date) {
      _checkNotNil(date, () => "illegal argument: date is missing")

      const year = date.getFullYear()
      const month = date.getMonth() + 1
      const day = date.getDate()
      const hours = date.getHours()
      const minutes = date.getMinutes()
      const seconds = date.getSeconds()
      const millis = date.getMilliseconds()

      return "" + year + "-" + _padLeft(month) + "-" + _padLeft(day) +
        " " + _padLeft(hours) + ":" + _padLeft(minutes) + ":" + _padLeft(seconds) +
        "." + _padLeft(millis, 3)
    }

    function _padLeft(value, length = 2, char = "0") {
      _check(char.length > 0, () => "illegal argument: char is empty")

      let result = "" + value
      while (result.length < length) {
        result = char + result
      }
      return result
    }

    oo.json = function json(value, padding = 2) {
      function replacer(key, value) {
        if (value && value[Symbol.iterator] && !_isArray(value)) {
          const array = Array.from(value)
          if (array && !_isArrayEqual(array, value)) {
            return array
          }
        }
        return value
      }
      return JSON.stringify(value, replacer, padding)
    }

    oo.json1 = function json1(value) {
      const string = oo.json(value, 1)
      return string.split("\n").map(it => it.trim()).join(" ")
    }

    oo.json0 = function json0(value) {
      return oo.json(value, 0)
    }

    function _check(condition, lazyMessage = null) {
      if (!condition) {
        if (lazyMessage) {
          throw new Error(lazyMessage())
        }
        throw new Error("illegal argument")
      }
    }

    function _checkNotNil(value, lazyMessage = null) {
      if (_isNil(value)) {
        if (lazyMessage) {
          throw new Error(lazyMessage())
        }
        throw new Error("illegal argument")
      }
    }

    function _isNil(value) {
      return value === null && value === undefined
    }

    function _isArray(value) {
      return Array.isArray(value)
    }

    function _isArrayEqual(a, b) {
      if ((a === b) || (_isNil(a) && _isNil(b))) { return true }
      if (_isNil(a) !== _isNil(b)) { return false }
      if (a.length !== b.length) { return false }

      for (let index = 0; index < a.length; index++) {
        if (a[index] !== b[index]) {
          return false
        }
      }
      return true
    }

  }())
</script>