TypeScript Array map() Method

The Array.map() is an inbuilt TypeScript function that creates a new array with the results of calling a provided function on every element in the array.

Syntax:

array.map(callback[, thisObject])

Parameters:

This method accepts two parameters as mentioned above and described below: 

• callback: This parameter is the function that produces an element of the new Array from an element of the current one.
• thisObject: This is the Object to use as this parameter when executing callback.

Return Value:

This method returns the created array. 

Example 1: Applying a Mathematical Function: In this example we creates a number[] array, applies Math.log to each element using map().

// Driver code
let arr: number[] = [11, 89, 23, 7, 98];

// use of map() method
let val: number[] = arr.map(Math.log);

// printing element
console.log(val);

Output: 

[
  2.3978952727983707,
  4.48863636973214,
  3.1354942159291497,
  1.9459101490553132,
  4.584967478670572
]

Example 2: Mapping Elements with Their Indices: In this example we uses map() to iterate over arr, squaring each value. For each element.

// Driver code
let arr: number[] = [2, 5, 6, 3, 8, 9]; 

// use of map() method    
arr.map((val: number, index: number) => {
    // printing element
    console.log("key: ", index, "value: ", val * val);
});

Output: 

key :  0 value :  4
key :  1 value :  25
key :  2 value :  36
key :  3 value :  9
key :  4 value :  64
key :  5 value :  81