How to Add New Elements to an Array

How to append something to an array?

Use the Array.prototype.push method to append values to the end of an array:

// initialize array
var arr = [
  "Hi",
  "Hello",
  "Bonjour"
];

// append new value to the array
arr.push("Hola");

console.log(arr);

How to add new elements to an array?

The size of an array can't be modified. If you want a bigger array you have to instantiate a new one.

A better solution would be to use an ArrayList which can grow as you need it. The method ArrayList.toArray( T[] a ) gives you back your array if you need it in this form.

List<String> where = new ArrayList<String>();
where.add( ContactsContract.Contacts.HAS_PHONE_NUMBER+"=1" );
where.add( ContactsContract.Contacts.IN_VISIBLE_GROUP+"=1" );

If you need to convert it to a simple array...

String[] simpleArray = new String[ where.size() ];
where.toArray( simpleArray );

But most things you do with an array you can do with this ArrayList, too:

// iterate over the array
for( String oneItem : where ) {
    ...
}

// get specific items
where.get( 1 );

How to insert an item into an array at a specific index (JavaScript)

You want the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert).

In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join()); // Jani,Hege,Stale,Kai Jim,Borge
arr.splice(2, 0, "Lene");
console.log(arr.join()); // Jani,Hege,Lene,Stale,Kai Jim,Borge

How to insert a new element in array in c

You could add elements if your array is big enough and you manage its actual size manually (and make sure it stays below the max allocated size). You just have to copy all the elements above the insertion point to higher locations (based on how many items you want to insert), which is very inefficient. However, unlike linked data structures, you retain the benefits of working with an array that way.

There are data structures that combined the ~best of both worlds (more or less) by managing linked arrays, but they're more complicated to manage.

Simplest way to add an item to beginning of an array in Java

for(int i = roadVehicles.length; i > 0; i--) {
    if (roadVehicles[i-1] != null) {
        roadVehicles[i] = roadVehicles[i-1];                
    }
}
roadVehicles[0] = car;

How to extend an existing JavaScript array with another array, without creating a new array

The .push method can take multiple arguments. You can use the spread operator to pass all the elements of the second array as arguments to .push:

>>> a.push(...b)

If your browser does not support ECMAScript 6, you can use .apply instead:

>>> a.push.apply(a, b)

Or perhaps, if you think it's clearer:

>>> Array.prototype.push.apply(a,b)

Please note that all these solutions will fail with a stack overflow error if array b is too long (trouble starts at about 100,000 elements, depending on the browser).

If you cannot guarantee that b is short enough, you should use a standard loop-based technique described in the other answer.