map() creates a new array from calling a function for every array element. map() does not execute the function for empty elements. map() does not change the original array.

How to Create a Map. You can create a JavaScript Map by: Passing an Array to new Map() Create a Map and use Map.set()

JavaScript Map.groupBy() ES2024 added the Map.groupBy() method to JavaScript. The Map.groupBy() method groups elements of an object according to string values returned from a callback function.

JavaScript Function Syntax. A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses (). Function names can contain letters, digits, underscores, and dollar signs (same rules as variables). The parentheses may include parameter names separated by commas: (parameter1, parameter2, ...)

With arrow functions the this keyword always represents the object that defined the arrow function. Let us take a look at two examples to understand the difference. Both examples call a method twice, first when the page loads, and once again when the user clicks a button.

The map() function executes a specified function for each item in an iterable. The item is sent to the function as a parameter.

Learn more about Map objects, and the difference between a Map and an Array, in the the chapter: JavaScript Maps.

The array_map() function sends each value of an array to a user-made function, and returns an array with new values, given by the user-made function. Tip: You can assign one array to the function, or as many as you like.

To display the result in a map, you need access to a map service, like Google Maps. In the example below, the returned latitude and longitude is used to show the location in a Google Map (using a static image):

JavaScript References. W3Schools maintains a complete JavaScript reference, including all HTML and browser objects. The reference contains examples for all properties, methods and events, and is continuously updated according to the …