JavaScript. Cannot iterate an object with Object.keys () to get new

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I have an object at the input, how do I return the modified object on the basis of the existing one?

I used Object.keys() for this purpose in conjunction with the iterator map(). But something does not work, I get undefined.

let objjjj = {
  a: 2,
  b: 3,
  c: 4
}

console.log(
  Object.keys(objjjj).map((key, i) => {
    key: objjjj[key] + 1
  })
)

You need some parenthesis to wrap curly brackets in arrow functions.

Otherwise it is treated as block statement, where the standard return of undefined takes place.

For creating a single object, you could spread the single objects to Object.assign.

let object = { a: 2, b: 3, c: 4 };
    
console.log(
    Object.assign(...Object.keys(object).map((key, i) => ({ [key]: object[key] + 1 })))
);

forin, Objects created from built–in constructors like Array and Object have The loop will iterate over all enumerable properties of the object itself forEach() or the for​of loop) when iterating over arrays where the order of access is important. var obj = new ColoredTriangle(); for (const prop in obj) { if (obj. 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:

When you return an object from an arrow function is necessary that you surround it with parentheses:

let obj = {
  a: 2,
  b: 3,
  c: 4
}

console.log(
  Object.keys(obj)
  .reduce((acc, key) => ({
    ...acc,
    [key]: obj[key] + 1
  }), {})
)

// Or by using Object.entries


console.log(
  Object.entries(obj)
  .reduce((acc, [key, value]) => ({
    ...acc,
    [key]: value + 1
  }), {})
)

How to iterate over object properties in JavaScript, If you have an object, you can't just iterate it using map() , forEach() or a for..of loop. You will get errors: const items = { 'first': new Date(),  Syntax Object.keys(obj)Parameters obj The object of which the enumerable's own properties are to be returned. Return value. An array of strings that represent all the enumerable properties of the given object.

You need to return value instead to assign again to key.

let objjjj = {
  a: 2,
  b: 3,
  c: 4
}

console.log(
  Object.keys(objjjj).map((key, i) => {
    return objjjj[key] + 1
  })
)

Iterating through JavaScript Objects, Developers tend to know how to iterate through JavaScript Arrays easily but Object properties, besides a value , have three special attributes (also known as “​flags”): The Object.keys() method returns an array of Object keys. The benefits of developer communities cannot be over-emphasized in the  This tutorial will cover JavaScript Objects and show you how to Iterate through Object Keys and Values, otherwise known as looping through associative arrays with key, value pairs.

Iterating over arrays and objects in JavaScript, Iterating over arrays and objects in JavaScript It iterates over both array indices and property keys. function Person(name) { this.name = name; } Person.​prototype = { describe: function() { return "Name: "+this.name; } }; var person = new The methods don't have a result, but you can produce one in the  So we get a plain object with same key/values as the map. Set. A Set is a special type collection – “set of values” (without keys), where each value may occur only once. Its main methods are: new Set(iterable) – creates the set, and if an iterable object is provided (usually an array), copies values from it into the set.

Objects, A property is a “key: value” pair, where key is a string (also called a “property get property values of the object: alert ( user . name ) ; // John alert ( user . age ) ; // 30 The dot notation cannot be used in a similar way: to create a new object and replicate the structure of the existing one by iterating over its  Objects created from built–in constructors like Array and Object have inherited non–enumerable properties from Object.prototype and String.prototype, such as String's indexOf() method or Object's toString() method. The loop will iterate over all enumerable properties of the object itself and those the object inherits from its constructor's prototype (properties closer to the object in the prototype chain override prototypes' properties).

Looping through objects in JavaScript, Once in a while, you may need to loop through Objects in JavaScript. is Object.​entries because you get both the key and property values. Plain objects also support similar methods, but the syntax is a bit different. Object.keys, values, entries. For plain objects, the following methods are available: Object.keys(obj) – returns an array of keys. Object.values(obj) – returns an array of values. Object.entries(obj) – returns an array of [key, value] pairs.

Comments
  • Arrow functions returning an object must have said object in brackets, to distinguish from a code block. Also note the result your current code will be producing, with said brackets, is very peculiar. Most interesting is that you do not use computed property names, aka all objects will have a property called key. Last but least, you log an array of objects (one for each property), which doesn't sound like what you want at all.
  • Object.keys(objjjj).forEach(key => objjjj[key]++);
  • Thank you, but I need the new obj as it was, istead of creaing an extra objects inside. I mean const obj = { 'key': 3, "key": 4 ....}
  • it does not work with same keys. please add a possible alternative result.
  • I do not need the same keys. Just like in the question example above
  • and which key names do you want?
  • @J.Pichardo, it's just a new approach.