Angular: Function to calculate the length of string

isArray

var isArray = (function() {
  if (!isFunction(Array.isArray)) {
    return function(value) {
      return toString.call(value) === '[object Array]';
    };
  }
  return Array.isArray;
})();

isObject

function isObject(value){return value != null && typeof value === 'object';}

isString

function isString(value){return typeof value === 'string';}

size

/*
@param {Object|Array|string} obj Object, array, or string to inspect.
@param {boolean} [ownPropsOnly=false] Count only "own" properties in an object
@returns {number} The size of `obj` or `0` if `obj` is neither an object nor an array.
*/

function size(obj, ownPropsOnly) {
  var count = 0, key;

  if (isArray(obj) || isString(obj)) {
    return obj.length;
  } else if (isObject(obj)) {
    for (key in obj)
      if (!ownPropsOnly || obj.hasOwnProperty(key))
        count++;
  }

  return count;
}