Explain the Array functions in JavaScript
A JavaScript array can:
- Hold values of different types.
- The length of an array is dynamically sized and auto-growing.
Most of the array functions are used to transform or manipulate an array in some way.
In this post we will cover the following array functions:
- map()
- forEach()
- reduce()
- reduceRight()
map():
Takes an array, transforms its elements, and includes the results in a new array.
* * *
const array1 = [1, 4, 9, 16];
/ / pass a function to map
const map1 = array1.map(x =>x * 2);
console. log( map1);
// output: Array [2, 8, 18, 32]
forEach():
Executes a function on every element of an array.
* * *
let ranks = [‘A’ B ‘C’];
ranks.forEach( function (e) {
console. log(e);
});
/ / output: “A”
/ / output: “B”
/ / output: “C”
reduce():
Reduces an array into a value.
* * *
/ / calculate the total of elements of the array
let numbers = [1, 2, 3];
let sum = numbers.reduce( function (accumulator, current) {
return accumulator + current;
});
console. log( sum); / / 6
reduce():
The reducer function takes five arguments:
1.Accumulator: accumulates callback’s return
values.
2. Current Value: the current element being
processed.
3.Current Index (optional): the index of the current element being processed.
4. Source Array (optional): the array reduce) was called upon.
5. Initial Value (optional): the first argument to the first call of the callback. If no value is supplied, the first element in the array will be used.
reduceRight():
Works in the same way as the reduce() method, but in the opposite direction.
* * *
/ / calculate the total of elements of the array
let numbers = [1, 2, 3];
let sum= numbers.reduceRight( function (accumulator, current)
{
return accumulator + current;
});
console. log( sum) ; //6
