Check that value is object literal?

Question

I have a value and want to know if it\'s an iteratable object literal, before I iterate it.

How do I do that?

Answer 1

Vanilla Javascript version of JQuery.isPlainObject function.

var class2type = {};
var toString = class2type.toString;
var getProto = Object.getPrototypeOf;
var hasOwn = class2type.hasOwnProperty;
var fnToString = hasOwn.toString;
var ObjectFunctionString = fnToString.call(Object);

function isPlainObject(obj) {
  var proto, Ctor;

  // Detect obvious negatives
  // Use toString instead of jQuery.type to catch host objects
  if (!obj || toString.call(obj) !== "[object Object]") {
    return false;
  }

  proto = getProto(obj);

  // Objects with no prototype (e.g., `Object.create( null )`) are plain
  if (!proto) {
    return true;
  }

  // Objects with prototype are plain iff they were constructed by a global Object function
  Ctor = hasOwn.call(proto, "constructor") && proto.constructor;
  return typeof Ctor === "function" && fnToString.call(Ctor) === ObjectFunctionString;
}

Example:

isPlainObject({}) // true
isPlainObject( "test" ) // false