Arrays In Javascript
An array is an object. Many values contain an array. So, the array is important in javascript.
Arrays Syntex- const=['value', 'value', 'value']
Also can be written- Const a=[7, "string",
boollean]
Some example array codes-
let marks_class_12 = [91, 82, 63, 84, false, "Not
Present"]
print this- console.log(marks_class_12)
individual track the number
then code is:
console.log(marks_class_12[0])
console.log(marks_class_12[1])
console.log(marks_class_12[2])
console.log(marks_class_12[3])
console.log(marks_class_12[4])
console.log(marks_class_12[5])// index written rules. means position.
Here- 0, 1, 2, 3 array index
that means position
0-91
1-82
2-63
console.log(marks_class_12[6]) // Will be undefined because index 6
does not exist
Anyone can define [6]
then the code is
marks_class_12[6] = 89 // Adding a new value to the array
then do console.log
## If you want to change on
arrays any position-
marks_class_12[0] = 96 // Changing the value of an array
then type code- console.log(marks_class_12)
Here Full Code -
let marks_class_12 = [91, 82, 63,
84, false, "Not Present"]
console.log(marks_class_12[0])
console.log(marks_class_12[1])
console.log(marks_class_12[2])
console.log(marks_class_12[3])
console.log(marks_class_12[4])
console.log(marks_class_12[5])
console.log(marks_class_12[6]) //
Will be undefined because index 6 does not exist
console.log("The length of
marks_class_12 is", marks_class_12.length)
marks_class_12[6] = 89 // Adding
a new value to the array
marks_class_12[0] = 96 //
Changing the value of an array
console.log(marks_class_12)
Now 2 topics are very important
- 1. typeof
2. .length
typeof means - how are arrays??- object
or string or boolean
let marks_class_12 = [91, 82, 63, 84, false,
"Not Present"]
console.log(typeof marks_class_12)
.lenth means - how arrays
length? -
let marks_class_12 = [91, 82, 63, 84, false,
"Not Present"]
console.log("The length of
marks_class_12 is", marks_class_12.length)
Arrays Methods
we use this method to use easily our coding journey. Arrays methods are-
1. toString
2. join
3. Pop()
4. Push()
5. Shift
6. Unshift
7. Delete
8. Concat
9. Sort
10. Splice
11. Slice
12. Reverse
toString Method in Js
Convert an array to string and coma to separate value.
The Code Is-
let num = [1, 2, 3, 34, 4]
let b = num.toString() // b is now a string
return: console.log(b, typeof b)
1, 2, 3, 34, 4 string
Join Method in JS
Join all the arrays using a separator
The Code is-
let num = [1, 2, 3, 34, 4]
let b=num.join(" and ")
Return- console.log(b)
1 and 2 and 3 and 34 and 4
pop() Method
Remove the last element from a arrays
The Code Is- let num = [1, 2, 3, 34, 4]
let a= num.pop()
Return- console.log(num, a)
here- num: [1, 2, 3, 34]
a= 4
## Update is original arrays
## Return the popped of values
push() Method
Add a new element at the end of the arrays
The Code Is- let num = [4, 2, 4, 6, 8]
let d = num.push(7)
console.log(num, d)
Here print - num: [4, 2, 4, 6, 8, 7]
d= 7
## Modified original arrays
## Return this value
Shift() Method
Removes an element from the start of the array
The code is -let num = [4, 2, 4, 6, 8]
let a= num.shift()
console.log(num, a)
Here - num- [ 2, 4, 6, 8]
a= 4
## shift is changed original arrays
## Return the values
Unshift() Method
Add an element to the beginning and return the length of the new array
The code is- let num = [4, 2, 4, 6, 8]
let a= num.unshift(98)
console.log(num, a)
Here- num: [98, 4, 2, 4, 6, 8]
a= 5
Total Code-
let num = [4, 2, 4, 6, 8]
let a = num.toString() //sting method
console.log(a, typeof a)
let b = num.join(" and ") //join method
console.log(b, typeof b)
let c = num.pop()// pop method
console.log(num, c)
let d = num.push(7)
console.log(num, d)
let e= num.shift()
console.log(num, e)
let f= num.unshift(89)
console.log(num, f)
Delete Method ()
Delete is not a method. It’s an operator.
Arrays element can be deleted using the delete operator
Code is-
let num = [4, 2, 4,
6, 8]
delete num [0] //here
[]: means function and 0, 1, 2 : arrays index
Return: console.log (num)
##delete option use arrays does not change / arrays length
Concat()
Concat is an important arrays method. We use React.js,
Next.js, JS, Vanila.js, and Apps.
Concat just joins 2 or more arrays.
Code is-
let a = [ 1, 2];
let b = [3, 4];
let c = [5, 6];
a.concat (b, c)
return=[1,2,3,4,5,6]
##Return a new arrays
## Does not the existing arrays
let num2=[10, 11, 12]
let newarrays=num.concat(num2)
console.log(newarrays)
Sort ()
1. Help arrange alphabetic order
2. Modified the original arrays
Code is-
let num = [4, 2, 4, 6, 8]
num.sort()
console.log (num)
We arrange it in ascending order and then use compare function
let compare= (a, b)=>{
return (a-b)
}
let num = [4, 2, 4, 6, 8]
num.sort(compare)
console.log (num)
Splice () Method
Splice can be used to add a new item to an array
Code is –
let num = [4, 2, 4, 6, 8]
num.splice (2, 6, 8)
console.log(num)
Here splice method start
Position to add, no element to remove, element to add
Here is all code
delete num[1] //delete operator
console.log(num)
let num2 = [10, 11, 12]
let newarrays = num.concat(num2)
console.log(newarrays)
num.sort()
console.log(num)
let compare = (a, b) => {
return (b - a)
}
let num3 = [7, 2, 4, 6, 8]
num3.sort(compare)
console.log(num3)
num.splice(0, 6, 8)
console.log(num)
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