Javascript Array Map — A Complete guide

Map is one of the most used Array method, from simple transformation logics to displaying list of items in React, we deep dive into all it can do

map

Syntax — array.map(function(iterateValue, index, array), thisValue)

Arguments —

• callback function (R)— this will be called for every items in the array
• thisValue (O) — Whatever value we pass here can be assesed with this inside the callback function

Callback function Arguments —

• iterateValue (O)— Value of the current element of the array
• index (O)— Index of the current element
• array (O) — Source array to the map method

R — Required , O — Optional Parameter

const marks = [98, 100, 50, 75, 90];
const callbackFn = function () {
  return 'Some Value';
}
const transformedMarks = marks.map(callbackFn);
console.log(transformedMarks); 
// ["Some Value","Some Value","Some Value","Some Value","Some Value"]

Code Analysis

• marks.map(callbackFn); — marks is the source array and we are passing the callbackFn as argument.
• marks array will be iterated and callback function will be called with each iteration
• Notice, we are having an empty callback and we are not using the value from the marks .
• Whatever we return from the callback…