Index Inside Map() Function
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...
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?
4 Answers
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:
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.
Array.prototype.map() index:
One can access the index Array.prototype.map() via the second argument of the callback function. Here is an example:
const array = [1, 2, 3, 4];
const map = array.map((x, index) => {
console.log(index);
return x + index;
});
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