javascript - How to check if an argument is an object? -

i know considered object in javascript. making function requires argument accepts in format:

{    a: 'b',    c: 'd' } 

so type of key value pair inside curly braces sort of object not other type of objects. how validate specifically?

update: after writing of below , later giving further thought, i'd suggest take @ trevor's answer. think more deserving of beautiful green checkmark answer, , here's why.

i took question @ face value , ran it: if want literally said, function $.isplainobject() way go. really need do? keep in mind $.isplainobject() not efficient function; enumerates through object's properties. , noted below, can't distinguish between {} , new object().

instead of that, trevor suggests checking properties need, , cases, of time, think he's right. it's closer approach take in own code: validate need, ignore rest.

so take @ answer , consider it. (and won't offended if move checkmark!)

now original answer:

there's $.isplainobject() function in jquery. if you're not using jquery, can copy source code function app. open jquery source , search isplainobject:.

it's worth reading source function in case, see isn't simple typeof or instanceof check:

isplainobject: function( obj ) {     // must object.     // because of ie, have check presence of constructor property.     // make sure dom nodes , window objects don't pass through,     if ( !obj || jquery.type(obj) !== "object" || obj.nodetype || jquery.iswindow( obj ) ) {         return false;     }      try {         // not own constructor property must object         if ( obj.constructor &&             !core_hasown.call(obj, "constructor") &&             !core_hasown.call(obj.constructor.prototype, "isprototypeof") ) {             return false;         }     } catch ( e ) {         // ie8,9 throw exceptions on host objects #9897         return false;     }      // own properties enumerated firstly, speed up,     // if last 1 own, properties own.      var key;     ( key in obj ) {}      return key === undefined || core_hasown.call( obj, key ); },  type: function( obj ) {     if ( obj == null ) {         return string( obj );     }     return typeof obj === "object" || typeof obj === "function" ?         class2type[ core_tostring.call(obj) ] || "object" :         typeof obj; },  iswindow: function( obj ) {     return obj != null && obj == obj.window; }, 

and there class2type object code uses:

// [[class]] -> type pairs class2type = {},  // populate class2type map jquery.each("boolean number string function array date regexp object error".split(" "), function(i, name) {     class2type[ "[object " + name + "]" ] = name.tolowercase(); }); 

(these code snippets out of context; you'd need tweak syntax if using them standalone.)

of course depending on circumstances, may not need all of these checks. , if you're using jquery already, can call $.isplainobject() , not sweat details.

also note not possible distinguish object literal object created new object:

var obj1 = { a:'b', c:'d' };  var obj2 = new object(); obj2.a = 'b'; obj2.c = 'd';  console.log( $.isplainobject(obj1) );  // prints true console.log( $.isplainobject(obj2) );  // prints true! 

they both return true $.isplainobject(), , i'm pretty sure other test devise unable tell which either.

a funny historical note: when john resig added function jquery in 2009, going call $.isobjectliteral(). @ urging changed name $.isplainobject because of ambiguity.