Arrays
JavaScript arrays are used to store multiple values in a single variable, which can hold more than one value at a time. Arrays are a special type of objects, So
typeof operator in JavaScript returns "object" for
arrays.
Arrays use
numbered indexes.
Example:
var names= ["Chanthan", "Jack", "Jhon"];
Arrays use
numbers to access its "elements". For this example,
names[0]
returns Chanthan.
Objects
Objects use
names to access its "members".
Objects use
named indexes.
Example: var person = {firstName:"Chanthan", lastName:"Ratn", age:25};
For this example,
person.firstName
returns Chanthan.
In array, If you use a named index, JavaScript will redefine
the array to a
standard object. After that,
all array methods and properties will produce
incorrect results.
Example:
var size = person.length; // person.length will
return 0
var name= person[0]; // person[0] will return undefined
So how to get the length of a object in JavaScript object (that is, associative array)
Object.size = function(obj) {
var size = 0, key;
for (key in obj) {
if (obj.hasOwnProperty(key)) size++;
}
return size;
};
//get the length of array object
var size = Object.size(array);
So,
When to Use Arrays. When to use Objects.
- JavaScript doesn't support associative arrays.
- Use objects when you want the element names to be
strings (text).
- Use arrays when you want the element names to be
numbers.
10:19 PM
