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Concept visual
Start at both ends
// Copies properties from a source object to a target object Object.assign(target, source) // Creates an object from an existing object Object.create(object)
Formula
// Returns an array of the key/value pairs of an objectObject.entries(object)
Formula
// Creates an object from a list of keys/valuesObject.fromEntries() // Returns an array of the keys of an object Object.keys(object) // Returns an array of the property values of an object Object.values(object) // Groups object elements according to a function Object.groupBy(object, callback) JavaScript Object.assign()
Object.assign() method copies properties from one or more source objects to a target object.
// Create Target Object const person1 = {
firstName: "John", lastName: "Doe", age: 50, eyeColor: "blue"
};
// Create Source Object const person2 = {firstName: "Anne",lastName: "Smith"};// Assign Source to Target
Object.assign(person1, person2);
JavaScript Object.entries()Object.entries() method to objects.
Formula
Object.entries() returns an array of the key/value pairs in an object:const person = {
firstName : "John", lastName : "Doe", age : 50, eyeColor : "blue"
};
let text = Object.entries(person);
Object.entries()makes it simple to use objects in loops:
const fruits = {Bananas:300, Oranges:200, Apples:500};
let text = "";
for (let [fruit, value] of Object.entries(fruits)) {
text += fruit + ": " + value + "<br>";
}
Object.entries()also makes it simple to convert objects to maps:
const fruits = {Bananas:300, Oranges:200, Apples:500};
const myMap = new Map(Object.entries(fruits));
Object.entries()is supported in all modern browsers since March 2017: JavaScript Object.fromEntries()
Formula
method creates an object from a list of key/value pairs.const fruits = [
["apples", 300],
["pears", 900],
["bananas", 500]
];
const myObj = Object.fromEntries(fruits);
JavaScript Object.values()
Object.values()is similar to Object.entries(), but returns a single dimension array of the object values:
const person = {
firstName : "John", lastName : "Doe", age : 50, eyeColor : "blue"
};
let text = Object.values(person);
Object.values()is supported in all modern browsers since March 2017: JavaScript Object.groupBy()
Object.groupBy() method to JavaScript.
Object.groupBy() method groups elements of an object according to string values returned from a callback function.
Object.groupBy() method does not change the original object.
// Create an Array const fruits = [
{name:"apples", quantity:300},
{name:"bananas", quantity:500},
{name:"oranges", quantity:200},
{name:"kiwi", quantity:150}
];
// Callback function to Group Elements function myCallback({ quantity }) {
return quantity > 200 ? "ok" : "low";
}
// Group by Quantity const result = Object.groupBy(fruits, myCallback);Object.groupby() is an ECMAScript 2024 feature. JavaScript 2024 is supported in new browsers since
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