How to Get Index Inside map() in JavaScript
How can we get the index of the current iteration inside a map()
function?
Example scenario#
Suppose we have an array we want to iterate over using the map()
function.
const lst = [1, 2, 3];
lst.map((elem) => {
console.log(`Element: ${elem}`);
return elem;
});
How can we access the index of the current iteration inside the map()
callback function? Without a for
loop, this process isn’t as intuitive without reading the docs.
Getting the index in map()
#
We can get the index of the current iteration using the 2nd parameter of the map()
function.
const lst = [1, 2, 3];
lst.map((elem, index) => {
console.log(`Element: ${elem}`);
console.log(`Index: ${index}`);
return elem;
});
From the MDN Web Docs, the following are the parameters for the map()
function.
currentValue
: the current element being processed in the array.index
: the index of the current element being processed in the array.array
: the array map was called upon.