Key value pairs are stored in associative arrays. For example, a numerically indexed array might not be the ideal choice for storing a student’s marks from several subjects in an array. Instead, we might use the names of the subjects as the keys in our associative array, with their appropriate marks as the value.

Example:-

Output:–

Some Features of Associative Arrays?

Associative arrays are similar to numeric arrays in appearance, but differ in terms of index. An associative array’s index is a string that establishes a strong relationship between key and value.

For storing employee wages in an array, a numerically indexed array is not the ideal choice. Instead, you may create an associative list with the workers’ names as keys and their salary as the value.

• The variable’s name is “$variable name…”, the element’s access index number is “[‘key name’],” and the array element’s value is “value.”
• Consider the following scenario: you have a group of people and want to assign gender to each of them based on their names.
• You may achieve this by using an associative list.
• You can do so by using the code below.

Traversing the Associative Array:-

Loops may be used to go over associative arrays. The associative array can be looped through in two different ways. Using the for loop first, and then the foreach loop second.

Example:-

In this case, the array keys() function is used to identify indices with provided names, and the count() method is used to count the number of indices in associative arrays.

Output:-

Creating an associative array of mixed types:-

Output:-

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Arrays are collections of data elements with a common name. Arrays provide a framework for defining and accessing several data elements with a single identity, making data administration easier.

When dealing with several data elements, we use array.

How many types of Array?

• Numeric/Indexed Array:- In this array index will be represented by a number. By default numeric array index start from 0.
  Example:- $num [0] = “ScmGalaxy”;
• Associative Array:- In this Array index/key will be represented by a string.
  Example:- $fees [“ScmGalaxy”] = 500;
• Multidimensional Array:- Arrays of Arrays is known as multidimensional arrays.
  Example:- $num [0] [0] = 25;

Some Array Operators are :-

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Arrays are a collection of data items stored under a single name. Array provides a mechanism for declaring and accessing several data items with only one identifier, thereby simplifying the task of data management.

We use an array when we have to deal with multiple data items. Arrays are a special type of object. The typeof operator in JavaScript returns “object” for arrays.

Declaration and initialization of Array

• Using Array Literal

Syntax: – var array_name = [ ];

Declaration and initialization of Array

• Using Array Literal

Syntax: – var array_name = [value1, value2, value_n];

Declaration and initialization of Array

• Using Array Constructor

Syntax: – var array_name = new Array( );

Declaration and initialization of Array

• Using Array Constructor

This will create an empty array with 5 lengths. So this is not a good idea to use Array
Constructor if you have only a single numeric value.

Note – By default, the array starts with index 0.

Important Points

• JavaScript arrays are zero-indexed: the first element of an array is at index 0.
• Using an invalid index number returns undefined.
• It’s possible to quote the JavaScript array indexes as well (e.g., geek[‘2’] instead of geek[2]), although it’s not necessary.
• Arrays cannot use strings as element indexes but must use integers.
• There is no associative array in JavaScript. geek[“fees”] = 200;
• No advantage to use Array Constructor so better to use Array Literal for creating Arrays in JavaScript.

Accessing Array Elements

Accessing Array Elements

Access all at once

Modifying Array Elements

Removing Array Elements

Array elements can be removed using the delete operator. This operator sets the array element it is invoked on to undefined but does not change the array‟s length.

Syantx :- delete Array_name[index];
Ex:- delete dev[0];

Length Property

The length property retrieves the index of the next available position at the end of the array. The length property is automatically updated as new elements are added to the array. For this reason, length is commonly used to iterate through all elements of an array.

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The array operators are used to compare arrays. To compare various arrays, use the operations shown below. Make sure you’re using proper grammar.

• Operator Name Example Result
• + Union $x + $y Union of $x and $y
• == Equality $x == $y Returns true if $x and $y have the same key/value pairs
• === Identity $x === $y Returns true if $x and $y have the same key/value pairs in the same order and of the same types
• != Inequality $x != $y Returns true if $x is not equal to $y
• <> Inequality $x <> $y Returns true if $x is not equal to $y
• !== Non-identity $x !== $y Returns true if $x is not identical to $y

Example:-

Output:-

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