I am missing a option how to get the index number inside the map
function using List
from Immutable.js
:
var list2 = list1.map(mapper => { a: mapper.a, b: mapper.index??? }).toList();
Documentation shows that map()
returns Iterable<number, M>
. Is there any elegant way to what I need?
You will be able to get the current iteration's index
for the map
method through its 2nd parameter.
Example:
const list = [ 'h', 'e', 'l', 'l', 'o'];
list.map((currElement, index) => {
console.log("The current iteration is: " + index);
console.log("The current element is: " + currElement);
console.log("\n");
return currElement; //equivalent to list[index]
});
Output:
The current iteration is: 0 <br>The current element is: h
The current iteration is: 1 <br>The current element is: e
The current iteration is: 2 <br>The current element is: l
The current iteration is: 3 <br>The current element is: l
The current iteration is: 4 <br>The current element is: o
See also: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/map
Parameters
callback - Function that produces an element of the new Array, taking three arguments:
1) currentValue
The current element being processed in the array.2) index
The index of the current element being processed in the array.3) array
The array map was called upon.