JavaScript Array Methods
Converting Arrays to Strings
The JavaScript method toString() converts an array to a string of (comma separated) array values.
var fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.toString();
TThe join() method also joins all array elements into a string. It behaves just like toString(), but in addition you can specify the separator:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.join(" * ");
Popping and Pushing
When you work with arrays, it is easy to remove elements and add new elements. This is what popping and pushing is:Popping items out of an array, or pushing items into an array.
Popping
The pop() method removes the last element from an array. The pop() method returns the value that was "popped out":
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.pop(); // Removes the last element ("Mango") from fruits
Pushing
The push() method adds a new element to an array (at the end). The push() method returns the new array length:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi"); // Adds a new element ("Kiwi") to fruits
Shifting Elements
Shifting is equivalent to popping, working on the first element instead of the last. The shift() method removes the first array element and "shifts" all other elements to a lower index.The shift() method returns the string that was "shifted out":
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift(); // Removes the first element "Banana" from fruits
The unshift() method adds a new element to an array (at the beginning), and "unshifts" older elements:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Lemon"); // Returns 5
Changing Elements
Array elements are accessed using their index number. Array indexes start with 0. [0] is the first array element, [1] is the second, [2] is the third ...
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits[0] = "Kiwi"; // Changes the first element of fruits to "Kiwi"
The length property provides an easy way to append a new element to an array:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits[fruits.length] = "Kiwi"; // Appends "Kiwi" to fruits
Deleting Elements
Since JavaScript arrays are objects, elements can be deleted by using the JavaScript operator delete. Using delete may leave undefined holes in the array. Use pop() or shift() instead.
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.length; // the length of fruits is 4
Splicing an Array
The splice() method can be used to add new items to an array.
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2, 0, "Lemon", "Kiwi");
The splice() method returns an array with the deleted items:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2, 0, "Lemon", "Kiwi");
Using splice() to Remove Elements
With clever parameter setting, you can use splice() to remove elements without leaving "holes" in the array:
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(0, 1); // Removes the first element of fruits
Merging (Concatenating) Arrays
The concat() method creates a new array by merging (concatenating) existing array
var myGirls = ["Cecilie", "Lone"];
var myBoys = ["Emil", "Tobias", "Linus"];
var myChildren = myGirls.concat(myBoys); // Concatenates (joins) myGirls and myBoys
The concat() method does not change the existing arrays. It always returns a new array. The concat() method can take any number of array arguments:
var arr1 = ["Cecilie", "Lone"];
var arr2 = ["Emil", "Tobias", "Linus"];
var arr3 = ["Robin", "Morgan"];
var myChildren = arr1.concat(arr2, arr3); // Concatenates arr1 with arr2 and arr3
var arr1 = ["Emil", "Tobias", "Linus"];
var myChildren = arr1.concat("Peter");
Slicing an Array
The slice() method slices out a piece of an array into a new array.
var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(1);
The slice() method creates a new array. It does not remove any elements from the source array.
var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(3);
The slice() method can take two arguments like slice(1, 3).The method then selects elements from the start argument, and up to (but not including) the end argument.
var fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"];
var citrus = fruits.slice(1, 3);
Automatic toString()
JavaScript automatically converts an array to a comma separated string when a primitive value is expected.
This is always the case when you try to output an array.
var fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.toString();
All JavaScript objects have a toString() method.
Finding Max and Min Values in an Array
There are no built-in functions for finding the highest or lowest value in a JavaScript array.
