JavaScript Arrays
An array is a way of storing list of data
Defining Arrays
Array Constructor
var arrayname = new Array(); creates empty array
var student = new Array(5); creates array with 5 items
It is not necessary to set the length of an array, it can vary as needed during script execution.
Values can be assigned as array is declared
var student = new Array(“aaa”,”bbb”,”ccc”);
Javascript allows arrays to have values of different data types
var answers = new Array(10,”Yes”,21.23);
Arrays Literal Notation
Array literal notation provides a shorter method of defining arrays rather than using constructor.
var student = [];
var student = [“aaa”,”bbb”,”ccc”];
var answers = [10,”Yes”,21.23];
Accessing Arrays
Array Index is used to access array elements. The array index starts with 0 index.
answer[0] is 10
answer[1] is “Yes”
Length property
The length property is used to obtain the length of an array
student.length will give 3
for(var i=0;i<student.length;i++)
Changing Values:
student[1] = “zzz”;
Changing Length:
var student = [“aaa”,”bbb”,”ccc”];
student.length = 2;
array originally had 3 items but now has 2 items
var student = [“aaa”,”bbb”,”ccc”];
student.length = 5;
The array will now have 5 items, and last two items are undefined until values are assigned.
Properties of Arrays
constructor
index
length
Methods of Arrays
join() Method
join([separator]);
var student = [“aaa”,”bbb”,”ccc”];
var msg = student.join(“,”); result aaa,bbb,ccc
pop() method is used to remove last item from an array, and return last item
var student = [“aaa”,”bbb”,”ccc”];
student.pop();
student = [“aaa”,”bbb”];
push() method is used to add items at the end of an array
var student = [“aaa”,”bbb”,”ccc”];
student.push(“zzz”); student.push(“zzz”,”yyy”,”xxx”);
var student = [“aaa”,”bbb”,”ccc”,”zzz”];
shift() method is used to remove first item from an array and return the value
unshift() method is used to add items to the beginning of an array
reverse() method is used reverse the order of items in an array
sort() method converts each array item in to string value and the arrange items in ascending order based on string values
concat() method is used to concatenate
var student = [“aaa”,”bbb”,”ccc”];
var staff = [“xxx”,”yyy”];
var all = student.concat(staff); [“aaa”,”bbb”,”ccc”,”xxx”,”yyy”];
var student = [“aaa”,”bbb”,”ccc”];
var staff = [“xxx”,”yyy”];
var all = student.concat(staff,“zzz”,”111”];
result [“aaa”,”bbb”,”ccc”,”xxx”,”yyy”,”zzz”,”111”];
slice() method is used to slice specific portion of an array
arrayname.slice(start,stop); start is index were starts slice and stop is index after the last item you want to slice
var student = [“aaa”,”bbb”,”ccc”,”xxx”,”yyy”];
var result = student.slice(1,3); result = [”bbb”,”ccc”];
splice() method removes or replaces items
var student = [“aaa”,”bbb”,”ccc”,”xxx”,”yyy”];
student.splice(2,1); result = [“aaa”,”bbb”,”xxx”,”yyy”];
var student = [“aaa”,”bbb”,”ccc”,”xxx”,”yyy”];
student.splice(2,1,”zzz”); result = [“aaa”,”bbb”,”zzz”,”xxx”,”yyy”];
indexOf() method
var student = [“aaa”,”bbb”,”ccc”,”xxx”,”bbb”];
indexOf(“ccc”) returns 2
lastIndexOf() method
var student = [“aaa”,”bbb”,”ccc”,”xxx”,”bbb”];
student.lastIndexOf(“bbb”) returns 4
Nesting of Arrays
var student = [ [“aaa”, 60],
[”bbb”, 70],
[”ccc”, 80]
];
var student = new Array( new Array(“aaa”, 60),
new Array(”bbb”, 70),
new Array(”ccc”, 80)
);
Accessing
var i = 0;
var j = 0;
for(i=0;i<student.length;i++)
{
for(j=0;j<student[i].length;j++)
{
student[i][j];
}
}