Syntax, Parameter and Return Value
Syntax:
_.map(collection, [iteratee=_.identity])
Parameters:
-
collection (Array|Object|string): The collection to iterate over.
- [iteratee=_.identity] (Function): The function invoked per iteration.
Return Value:
(Array) - Returns the new mapped array.
Examples
Mapping Array Elements:
JavaScript
var _ = require('lodash');
var numbers = [1, 2, 3];
var doubled = _.map(numbers, n => n * 2);
console.log(doubled);
You can also try this code with Online Javascript Compiler
Output:
[2, 4, 6]
Demonstrates multiplying each number in an array.
Extracting Properties from Objects:
JavaScript
var users = [{ 'user': 'barney', 'age': 36 },
{ 'user': 'fred', 'age': 40 }];
var ages = _.map(users, 'age');
console.log(ages);
You can also try this code with Online Javascript Compiler
Output:
[36, 40]
Shows how to extract a specific property from each object in an array.
Mapping Over an Object:
JavaScript
var object = { 'a': 1, 'b': 2, 'c': 3 };
var valuesSquared = _.map(object, n => n * n);
console.log(valuesSquared);
You can also try this code with Online Javascript Compiler
Output:
[1, 4, 9]
An example of applying a function to each value in an object.
Mapping Over a String:
JavaScript
var string = "hello";
var asciiValues = _.map(string, char => char.charCodeAt(0));
console.log(asciiValues);
You can also try this code with Online Javascript Compiler
Output:
[104, 101, 108, 108, 111]
Demonstrates mapping each character in a string to its ASCII value.
Frequently Asked Questions
How does _.map() differ from native JavaScript Array.map()?
Lodash's _.map() works with a broader range of collections, including objects and strings, whereas the native Array.map() is limited to arrays.
Can _.map() modify the original collection?
No, _.map() returns a new array and does not modify the original collection, adhering to the principles of functional programming.
Is _.map() efficient for large datasets?
_.map() is generally efficient for large datasets, but performance depends on the complexity of the iteratee function and the size of the dataset.
Conclusion
Lodash's _.map() method is a versatile and essential tool for transforming collections in JavaScript. It offers a concise and readable way to apply a function to each element of a collection, producing a new array of transformed elements.
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