#Javascript: Using the Array.prototype.map() function.

Dennis Mathenge — Tue, 19 Nov 2019 16:18:02 +0000

When working with JavaScript arrays, you might want to create a new array with the results of calling a provided function on every element in the previous/original array.

JavaScript has a very nifty function called Array.prototype.map() that you can use to do this.

Array.prototype.map() accepts a callback function as a parameter.

The callback function produces an element of the new Array and takes three arguments:

currentValue - This is the current element being processed in the array.
index (optional) - This is the index of the current element being processed in the array.
array (optional) - The original array that map was called upon.
thisArg (optional) - Value that you can use as this when executing the callback

Example usage:

const names = ['mike', 'john', 'anne'];
const namesUppercase = names.map(name => name.toUpperCase());
console.log(namesUppercase);
namesUppercase = ["MIKE", "JOHN", "ANNE"]

DEV Community: Dennis Mathenge

#Javascript: Using the Array.prototype.map() function.

Example usage: