util functions in vue/packages/vue-template-compiler/build.js

util-functions.js

/**
 * Define a property.
 */
function def (obj, key, val, enumerable) {
  Object.defineProperty(obj, key, {
    value: val,
    enumerable: !!enumerable,
    writable: true,
    configurable: true
  });
}

// explicitness and function inlining.
function isUndef (v) {
  return v === undefined || v === null
}

/**
 * Check if value is primitive.
 */
function isPrimitive (value) {
  return (
    typeof value === 'string' ||
    typeof value === 'number' ||
    typeof value === 'symbol' ||
    typeof value === 'boolean'
  )
}

var _toString = Object.prototype.toString;

function toRawType (value) {
  return _toString.call(value).slice(8, -1)
}

/**
 * Strict object type check. Only returns true
 * for plain JavaScript objects.
 */
function isPlainObject (obj) {
  return _toString.call(obj) === '[object Object]'
}

/**
 * Make a map and return a function for checking if a key
 * is in that map.
 */
function makeMap (
  str,
  expectsLowerCase
) {
  var map = Object.create(null);
  var list = str.split(',');
  for (var i = 0; i < list.length; i++) {
    map[list[i]] = true;
  }
  return expectsLowerCase
    ? function (val) { return map[val.toLowerCase()]; }
    : function (val) { return map[val]; }
}

/**
 * Remove an item from an array.
 */
function remove (arr, item) {
  if (arr.length) {
    var index = arr.indexOf(item);
    if (index > -1) {
      return arr.splice(index, 1)
    }
  }
}

/**
 * Check whether an object has the property.
 */
var hasOwnProperty = Object.prototype.hasOwnProperty;
function hasOwn (obj, key) {
  return hasOwnProperty.call(obj, key)
}

/**
 * Create a cached version of a pure function.
 */
function cached (fn) {
  var cache = Object.create(null);
  return (function cachedFn (str) {
    var hit = cache[str];
    return hit || (cache[str] = fn(str))
  })
}

/**
 * Camelize a hyphen-delimited string.
 */
var camelizeRE = /-(\w)/g;
var camelize = cached(function (str) {
  return str.replace(camelizeRE, function (_, c) { return c ? c.toUpperCase() : ''; })
});

/**
 * Hyphenate a camelCase string.
 */
var hyphenateRE = /\B([A-Z])/g;
var hyphenate = cached(function (str) {
  return str.replace(hyphenateRE, '-$1').toLowerCase()
});

/**
 * Return the same value.
 */
var identity = function (_) { return _; };


/**
 * Simple bind polyfill for environments that do not support it,
 * e.g., PhantomJS 1.x. Technically, we don't need this anymore
 * since native bind is now performant enough in most browsers.
 * But removing it would mean breaking code that was able to run in
 * PhantomJS 1.x, so this must be kept for backward compatibility.
 */

/* istanbul ignore next */
function polyfillBind (fn, ctx) {
  function boundFn (a) {
    var l = arguments.length;
    return l
      ? l > 1
        ? fn.apply(ctx, arguments)
        : fn.call(ctx, a)
      : fn.call(ctx)
  }

  boundFn._length = fn.length;
  return boundFn
}

function nativeBind (fn, ctx) {
  return fn.bind(ctx)
}

var bind = Function.prototype.bind
  ? nativeBind
  : polyfillBind;

/**
 * Mix properties into target object.
 */
function extend (to, _from) {
  for (var key in _from) {
    to[key] = _from[key];
  }
  return to
}