vue/src/util/lang.js

var Dep = require('../observer/dep')

/**
 * Check is a string starts with $ or _
 *
 * @param {String} str
 * @return {Boolean}
 */

exports.isReserved = function (str) {
  var c = (str + '').charCodeAt(0)
  return c === 0x24 || c === 0x5F
}

/**
 * Guard text output, make sure undefined outputs
 * empty string
 *
 * @param {*} value
 * @return {String}
 */

exports.toString = function (value) {
  return value == null
    ? ''
    : value.toString()
}

/**
 * Check and convert possible numeric strings to numbers
 * before setting back to data
 *
 * @param {*} value
 * @return {*|Number}
 */

exports.toNumber = function (value) {
  if (typeof value !== 'string') {
    return value
  } else {
    var parsed = Number(value)
    return isNaN(parsed)
      ? value
      : parsed
  }
}

/**
 * Convert string boolean literals into real booleans.
 *
 * @param {*} value
 * @return {*|Boolean}
 */

exports.toBoolean = function (value) {
  return value === 'true'
    ? true
    : value === 'false'
      ? false
      : value
}

/**
 * Strip quotes from a string
 *
 * @param {String} str
 * @return {String | false}
 */

exports.stripQuotes = function (str) {
  var a = str.charCodeAt(0)
  var b = str.charCodeAt(str.length - 1)
  return a === b && (a === 0x22 || a === 0x27)
    ? str.slice(1, -1)
    : false
}

/**
 * Camelize a hyphen-delmited string.
 *
 * @param {String} str
 * @return {String}
 */

exports.camelize = function (str) {
  return str.replace(/-(\w)/g, toUpper)
}

function toUpper (_, c) {
  return c ? c.toUpperCase() : ''
}

/**
 * Hyphenate a camelCase string.
 *
 * @param {String} str
 * @return {String}
 */

exports.hyphenate = function (str) {
  return str
    .replace(/([a-z\d])([A-Z])/g, '$1-$2')
    .toLowerCase()
}

/**
 * Converts hyphen/underscore/slash delimitered names into
 * camelized classNames.
 *
 * e.g. my-component => MyComponent
 *      some_else    => SomeElse
 *      some/comp    => SomeComp
 *
 * @param {String} str
 * @return {String}
 */

var classifyRE = /(?:^|[-_\/])(\w)/g
exports.classify = function (str) {
  return str.replace(classifyRE, toUpper)
}

/**
 * Simple bind, faster than native
 *
 * @param {Function} fn
 * @param {Object} ctx
 * @return {Function}
 */

exports.bind = function (fn, ctx) {
  return function (a) {
    var l = arguments.length
    return l
      ? l > 1
        ? fn.apply(ctx, arguments)
        : fn.call(ctx, a)
      : fn.call(ctx)
  }
}

/**
 * Convert an Array-like object to a real Array.
 *
 * @param {Array-like} list
 * @param {Number} [start] - start index
 * @return {Array}
 */

exports.toArray = function (list, start) {
  start = start || 0
  var i = list.length - start
  var ret = new Array(i)
  while (i--) {
    ret[i] = list[i + start]
  }
  return ret
}

/**
 * Mix properties into target object.
 *
 * @param {Object} to
 * @param {Object} from
 */

exports.extend = function (to, from) {
  for (var key in from) {
    to[key] = from[key]
  }
  return to
}

/**
 * Quick object check - this is primarily used to tell
 * Objects from primitive values when we know the value
 * is a JSON-compliant type.
 *
 * @param {*} obj
 * @return {Boolean}
 */

exports.isObject = function (obj) {
  return obj !== null && typeof obj === 'object'
}

/**
 * Strict object type check. Only returns true
 * for plain JavaScript objects.
 *
 * @param {*} obj
 * @return {Boolean}
 */

var toString = Object.prototype.toString
var OBJECT_STRING = '[object Object]'
exports.isPlainObject = function (obj) {
  return toString.call(obj) === OBJECT_STRING
}

/**
 * Array type check.
 *
 * @param {*} obj
 * @return {Boolean}
 */

exports.isArray = Array.isArray

/**
 * Define a non-enumerable property
 *
 * @param {Object} obj
 * @param {String} key
 * @param {*} val
 * @param {Boolean} [enumerable]
 */

exports.define = function (obj, key, val, enumerable) {
  Object.defineProperty(obj, key, {
    value: val,
    enumerable: !!enumerable,
    writable: true,
    configurable: true
  })
}

/**
 * Define a reactive property.
 *
 * @param {Object} obj
 * @param {String} key
 * @param {*} val
 */

exports.defineReactive = function (obj, key, val) {
  var dep = new Dep()
  Object.defineProperty(obj, key, {
    get: function metaGetter () {
      if (Dep.target) {
        dep.depend()
      }
      return val
    },
    set: function metaSetter (newVal) {
      if (val !== newVal) {
        val = newVal
        dep.notify()
      }
    }
  })
}

/**
 * Debounce a function so it only gets called after the
 * input stops arriving after the given wait period.
 *
 * @param {Function} func
 * @param {Number} wait
 * @return {Function} - the debounced function
 */

exports.debounce = function (func, wait) {
  var timeout, args, context, timestamp, result
  var later = function () {
    var last = Date.now() - timestamp
    if (last < wait && last >= 0) {
      timeout = setTimeout(later, wait - last)
    } else {
      timeout = null
      result = func.apply(context, args)
      if (!timeout) context = args = null
    }
  }
  return function () {
    context = this
    args = arguments
    timestamp = Date.now()
    if (!timeout) {
      timeout = setTimeout(later, wait)
    }
    return result
  }
}

/**
 * Manual indexOf because it's slightly faster than
 * native.
 *
 * @param {Array} arr
 * @param {*} obj
 */

exports.indexOf = function (arr, obj) {
  var i = arr.length
  while (i--) {
    if (arr[i] === obj) return i
  }
  return -1
}

/**
 * Make a cancellable version of an async callback.
 *
 * @param {Function} fn
 * @return {Function}
 */

exports.cancellable = function (fn) {
  var cb = function () {
    if (!cb.cancelled) {
      return fn.apply(this, arguments)
    }
  }
  cb.cancel = function () {
    cb.cancelled = true
  }
  return cb
}

/**
 * Check if two values are loosely equal - that is,
 * if they are plain objects, do they have the same shape?
 *
 * @param {*} a
 * @param {*} b
 * @return {Boolean}
 */

exports.looseEqual = function (a, b) {
  /* eslint-disable eqeqeq */
  return a == b || (
    exports.isObject(a) && exports.isObject(b)
      ? JSON.stringify(a) === JSON.stringify(b)
      : false
  )
  /* eslint-enable eqeqeq */
}