Most Useful Javascript Array Methods
Array Sorting
String Array Sorting
Sort method is used to sort array elements in ascending order.
var fruitsArray = ['Lemon','Mango','Orange','Apple'];
fruitsArray.sort();
console.log(fruitsArray);
Output: [ 'Apple', 'Lemon', 'Mango', 'Orange' ]
You can sort array in descending order by using reverse method. First sort array then reverse its element as
var fruitsArray = ['Lemon','Mango','Orange','Apple'];
fruitsArray.sort();
fruitsArray.reverse();
console.log(fruitsArray);
Output: [ 'Orange', 'Mango', 'Lemon', 'Apple' ]
Number Array Sorting
By default, sort method is used to sort string array only. To sort numeric array, we just have to pass a compare function to sort function as parameter. Below is ascending order sorting of numeric array.
Output: [ 2, 5, 6, 8, 9 ]
To sort numeric array in descending order, just return y-x as
var numbers = [6,8,2,5,9];
numbers.sort(function(x,y){
return y-x;
})
console.log(numbers);
Output: [ 9, 8, 6, 5, 2 ]
Array Find Largest & Smallest number
Highest number in numeric can be found by Math.max.apply method as
Output: 9
Similarly you can find smallest number by Math.min.apply method as
var numbers = [6,8,2,5,9];
var minNumber = Math.min.apply(null,numbers);
console.log(minNumber);
Output: 2
Javascript Map Array
Array map method get a callback function as parameter. On each element of array, this function is called.
Below three parameters are passed to this function. You can use 1 or 2 or all parameters.
- Array element
- Index of element
- Array itself
In below example, map method of array multiply each element of array by 2 and show in console. We are omitting array parameter as not being used in callback function.
var numbers = [6,3,9,2];
numbers.map(multiplyByTwo);
function multiplyByTwo(element, index){
console.log('Element at index '+index+ ' is '+element);
}
Output:
Element at index 1 is 3
Element at index 2 is 9
Element at index 3 is 2
Javascript Filter Method
Filter method apply to an array. It creates a new array based on certain condition. Like map method, filter method also gets a callback function on every element of array that can use three parameters.
In below example, callback function return even numbers of array. Here we omit parameters index and array as not being used.
6
2
6
12
Reduce Method Javascript
Reduce method calls a callback function on every element of array and reduce the array to a single value without changing the original array.
Callback function takes 4 parameters
- Total (sum till previous element)
- Element
- Index of element
- Array itself
Below example adds all elements of array and return it. Here callback function does not use index and array parameter so omit them.
Output: 23
Array Every Method
Every method operates on every element of array and return true if all elements meet a certain condition.
Output: false
Output is false as element 4 is not less then 4 so every method returns false.
Javascript Array Some
Some method return true if some elements of array meet a certain condition.
var numbers = [5,9,4,8];
function lessThanSix(element){
return element < 6;
}
var result = numbers.some(lessThanSix);
console.log(result);
Output: true
Output is true as some elements meet the condition
Find Array Method
Javascript array find method returns the value of first element that meets the condition.
var numbers = [7,9,4,8];
function lessThanSix(element){
return element < 6;
}
var result = numbers.find(lessThanSix);
console.log(result);
Output: 4
Array FindIndex
findIndex method returns index of first element that meets the certain condition.
Output: 2 (as element 4 is at index 2)
Post a Comment