How to loop through a plain JavaScript object with the objects as members?

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How can I loop through all members in a JavaScript object including values that are objects.

For example, how could I loop through this (accessing the "your_name" and "your_message" for each)?

var validation_messages = {
    "key_1": {
        "your_name": "jimmy",
        "your_msg": "hello world"
    },
    "key_2": {
        "your_name": "billy",
        "your_msg": "foo equals bar"
    }
}
for (var key in validation_messages) {
    // skip loop if the property is from prototype
    if (!validation_messages.hasOwnProperty(key)) continue;

    var obj = validation_messages[key];
    for (var prop in obj) {
        // skip loop if the property is from prototype
        if (!obj.hasOwnProperty(prop)) continue;

        // your code
        alert(prop + " = " + obj[prop]);
    }
}

The ES6 way to loop through objects with vanilla JavaScript, To achieve something similar, we can use the Object.keys() method, which returns an array of the keys in an object. Then we run that through  Loop through a plain JavaScript object with objects as members March 31, 2020; Playing the Chrome Dino Game March 20, 2020; Reporting All Exceptions in Your Website March 19, 2020; Custom exception with ZF2 March 19, 2020; Top 5 : Best open source PDF generation libraries for PHP March 16, 2020; Archives. March 2020 (6) February 2020 (1

Under ECMAScript 5, you can combine Object.keys() and Array.prototype.forEach():

var obj = {
  first: "John",
  last: "Doe"
};

//
//	Visit non-inherited enumerable keys
//
Object.keys(obj).forEach(function(key) {

  console.log(key, obj[key]);

});

Looping through objects in JavaScript, How do you check if a key is in an object JavaScript? A better way to loop through objects. The better way to loop through objects is first to convert the object into an array. Then, you loop through the array. You can convert an object into an array with three methods: Object.keys; Object.values; Object.entries; Object.keys. Object.keys creates an array that contains the properties of an object. Here’s an example.

The problem with this

for (var key in validation_messages) {
   var obj = validation_messages[key];
   for (var prop in obj) {
      alert(prop + " = " + obj[prop]);
   }
}

is that you’ll also loop through the primitive object's prototype.

With this one you will avoid it:

for (var key in validation_messages) {
   if (validation_messages.hasOwnProperty(key)) {
      var obj = validation_messages[key];
      for (var prop in obj) {
         if (obj.hasOwnProperty(prop)) {
            alert(prop + " = " + obj[prop]);
         }
      }
   }
}

A simple forEach() implementation for Arrays, Objects and NodeLists , and value as the value associated with the property key. A better way to loop through objects. The better way to loop through objects is first to convert the object into an array. Then, you loop through the array. You can convert an object into an array with three methods: Object.keys; Object.values; Object.entries; Object.keys. Object.keys creates an array that contains the properties of an object. Here’s an example.

In ES6/2015 you can loop through an object like this: (using arrow function)

Object.keys(myObj).forEach(key => {
  console.log(key);        // the name of the current key.
  console.log(myObj[key]); // the value of the current key.
});

jsbin

In ES7/2016 you can use Object.entries instead of Object.keys and loop through an object like this:

Object.entries(myObj).forEach(([key, val]) => {
  console.log(key); // the name of the current key.
  console.log(val); // the value of the current key.
});

The above would also work as a one-liner:

Object.entries(myObj).forEach(([key, val]) => console.log(key, val));

jsbin

In case you want to loop through nested objects as well, you can use a recursive function (ES6):

const loopNestedObj = obj => {
  Object.keys(obj).forEach(key => {
    if (obj[key] && typeof obj[key] === "object") loopNestedObj(obj[key]); // recurse.
    else console.log(key, obj[key]); // or do something with key and val.
  });
};

jsbin

Same as function above, but with ES7 Object.entries() instead of Object.keys():

const loopNestedObj = obj => {
  Object.entries(obj).forEach(([key, val]) => {
    if (val && typeof val === "object") loopNestedObj(val); // recurse.
    else console.log(key, val); // or do something with key and val.
  });
};

Here we loop through nested objects change values and return a new object in one go using Object.entries() combined with Object.fromEntries() (ES10/2019):

const loopNestedObj = obj =>
  Object.fromEntries(
    Object.entries(obj).map(([key, val]) => {
      if (val && typeof val === "object") [key, loopNestedObj(val)]; // recurse
      else [key, updateMyVal(val)]; // or do something with key and val.
    })
  );

Check If an Object Contains a Key using Javascript, The Object.entries() method returns an array of a given object's own is that a for​in loop enumerates properties in the prototype chain as well). An object is a JavaScript data type, just as a number or a string is also a data type. As a data type, an object can be contained in a variable. There are two ways to construct an object in JavaScript: The object literal, which uses curly brackets: {}. The object constructor, which uses the new keyword.

Using Underscore.js’s _.each:

_.each(validation_messages, function(value, key){
    _.each(value, function(value, key){
        console.log(value);
    });
});

JavaScript Object.fromEntries() Method, Objects created from built–in constructors like Array and Object have The loop will iterate over all enumerable properties of the object itself  meals is a regular plain JavaScript object. The object keys are taken using Object.keys(meals) and in a for..of loop enumerated. The code looks pretty simple, however, it can be optimized by removing the line let mealName = meals[key]. The optimization is possible by applying direct access to object property values using Object.values(). Now the property accessor line can be removed:

Object.entries(), It happens a lot that you need to loop over an Array with JavaScript Objects! But sometimes you just don't know what kind of properties that Object has. In this  This is not related to JSON, which is a data exchange format, but simply to JavaScript objects. – Felix Kling Jan 3 '12 at 16:46 @FelixKling and John, this question is distinct from the others.

forin, values() and Object.entries(). The main idea is the convert the object into an array and use array looping methods to loop through that array. Let's begin with the  I'm using Canvas to play and learn with Javascript. Currently I'm creating a circle and have it display in random areas on the screen. I was able to complete that exercise completely; everything ran smoothly in one function. Now I would like to create an object for the circle and call it in the for loop.

3 Methods to Loop Over Object Properties in JavaScript in Seconds, It happens a lot that you need to loop over an Array with JavaScript Objects! But sometimes you just don't know what kind of properties that  Unlike for in, for of works only with the iterable objects of javascript. Arrays, Maps, Sets and Strings(treated as a char array) are some of the iterable objects available in Javascript. Unlike for in, order of the elements is guaranteed in for of. Technique 4 : forEach Being a function call, this semantic of this technique is entirely differe…

Comments
  • possible duplicate of Loop through JavaScript object
  • Internet Explorer does not agree (sigh), says "Object does not support this property or method" when you do obj[prop]. I have yet to find a solution to this.
  • @MildFuzz actually it makes sense if you consider that JS objects do not necessary have numerical keys. You can't just iterate through an object. JS's for in is very similar to a traditional foreach.
  • for...in is a good solution, but if you use promises in the for()-loop be careful, because if you create a var in the loop, you can't use it in the promise' then-function. You var in the loop exists only one time, so it has in every then-function the same, even the last value. If you have that problem, try "Object.keys(obj).forEach" or my answer below.
  • +1 for brevity of code but apparently, doesn't perform as efficient as a for surprisingly. JSPerf - for in vs Object.keys
  • Beware of this error using this approach: "TypeError: Object.keys called on non-object". The for ... in ... hasOwnProperty pattern can be called on anything, as far as I can tell (object, array, null, undefined, true, false, number primitive, objects).
  • Note that IE7 doesn't support this.
  • @techiev2 those tests were never valid. See my updated ones for the current state of performance: jsperf.com/objdir/20
  • @techiev2: it's not Object.keys() which makes it slow, it's rather the forEach() and the repeated access to .length! If you use a classic for-loop instead, it's almost twice as fast as for..in + hasOwnProperty() in Firefox 33.
  • In short: check hasOwnProperty inside your for-in loops.
  • Note that this is only necessary if your object HAS prototype methods. For example, if the object you're looping through is just a JSON object, you won't need this check.
  • @rednaw To be safe I use that check because Object.prototype can be modified. No sane script would do that, but you cannot control what scripts might be run in your page by insane browser extensions. Browser extensions run in your page (on most browsers) and they can cause odd problems (e.g. set window.setTimeout to null!).
  • Thank you so much