如何在 Javascript 中匹配一个空字典？

Since it has no attributes, a for loop won't have anything to iterate over. To give credit where it's due, I found this suggestion here.

function isEmpty(ob){
for(var i in ob){ return false;}
return true;
}


isEmpty({a:1}) // false
isEmpty({}) // true

You'd have to check that it was of type 'object' like so:

(typeof(d) === 'object')

And then implement a short 'size' function to check it's empty, as mentioned here.

function isEmpty(obj) {
return Object.keys(obj).length === 0;
}

You could extend Object.prototype with this isEmpty method to check whether an object has no own properties:

Object.prototype.isEmpty = function() {
for (var prop in this) if (this.hasOwnProperty(prop)) return false;
return true;
};

If you try this on Node.js use this snippet, based on this code here

Object.defineProperty(Object.prototype, "isEmpty", {
enumerable: false,
value: function() {
for (var prop in this) if (this.hasOwnProperty(prop)) return false;
return true;
}
}
);

This is what jQuery uses, works just fine. Though this does require the jQuery script to use isEmptyObject.

isEmptyObject: function( obj ) {
for ( var name in obj ) {
return false;
}
return true;
}


//Example
var temp = {};
$.isEmptyObject(temp); // returns True
temp ['a'] = 'some data';
$.isEmptyObject(temp); // returns False

If including jQuery is not an option, simply create a separate pure javascript function.

function isEmptyObject( obj ) {
for ( var name in obj ) {
return false;
}
return true;
}


//Example
var temp = {};
isEmptyObject(temp); // returns True
temp ['b'] = 'some data';
isEmptyObject(temp); // returns False

How about using jQuery?

$.isEmptyObject(d)

I'm far from a JavaScript scholar, but does the following work?

if (Object.getOwnPropertyNames(d).length == 0) {
// object is empty
}

It has the advantage of being a one line pure function call.

var SomeDictionary = {};
if(jQuery.isEmptyObject(SomeDictionary))
// Write some code for dictionary is empty condition
else
// Write some code for dictionary not empty condition

This Works fine.

If performance isn't a consideration, this is a simple method that's easy to remember:

JSON.stringify(obj) === '{}'

Obviously you don't want to be stringifying large objects in a loop, though.