Common JavaScript Manual/Data types - Arrays
Making Array
editFor making array it's better to use list literal because it's most popular and simple syntaxis
a = []; //Empty list
b = [1,2,3,4,5]; //List with 5 elements
Work with elements
editAnd so, we have an array 'b' with five numbers and the empty array 'a'.
a[0] = b[2]; //1
delete b[2]; //2
b[3] = 6; //3
- From array b - [1,2,3,4,5] get element with index 2 (Numeration in arrays starts from 0). Now array a = [2]
- We delete element with index 2 from array b. Now array b = [0,1,undefined,3,4].
- We change value of element with index 3 from array b. Now array b = [0,1,undefined,6,4].
Work with slices
editArray.slice(start,end) - returns array with elements of Array from start index to end index without element with index end.
a = [0,1,2,3,4,5,6,7];
b = a.slice(2,5); //2,3,4
If start or end is negative number then index of start or end equal (length of array + start or end).
a = [0,1,2,3,4,5,6,7];
b = a.slice(2,-2); //2,3,4,5 because length = 8 and 8 + (-2) = 6
Array.splice(start,number,elem...) - return slice with number of elements from Array from start and it deletes this elements from Array, and it replaces it's by elem
a = [0,1,2,3,4,5,6,7];
b = a.splice(2,3,0,1,0);
print(b); // 2,3,4
print(a); // 0,1,0,1,0,5,6,7
Stack and row
editYou can use any Array as stack or row for it there are 4 function.
Name | Action |
---|---|
Array.pop() | Delete and return last element of Array |
Array.push(elem...) | Insert elem to end of Array |
Array.shift() | Delete and return first element of Array |
Array.unshift(elem...) | Insert elem to start of Array |
For example:
Foo = [1,2,3,4,5];
Bar = Foo.pop(); //Bar = 5 , Foo = [1,2,3,4]
Foo.unshift(Bar); // Foo = [5,1,2,3,4]
Sorting and reverse
editAlso Array.sort([predicate]) - If predicate not defined then sort elements in Array in lexicographical order else sort element in Array by results of function predicate that gets two arguements and returns -1 if first argument less then second or 1 if second argument less then first or 0 if arguments equal.
Array.reverse() - reverse elements in Array
arr = [5,3,1,4,2];
arr.sort();
print(arr); //1,2,3,4,5
arr.reverse();
print(arr); //5,4,3,2,1
Concatenate and joining
editArray.concat(elem1...) - returns array that containg elements from Array and elem if elem[n] is array then to the array that returns are added all elements from elem[n].
Array.join([separator]) - returns string with all elements and separator before every, if separator not defined then separator = ","
arr1 = [0,1,2,3,4]
arr2 = [5,6,7,8,9]
elem = 10;
arr = arr1.concat(arr2,elem); //0,1,2,3,4,5,6,7,8,9,10
str = arr.join(';'); //0;1;2;3;4;5;6;7;8;9;10
print(str);
Length of Array
editArray.length - number of elements in Array
arr = [0,1,2,3,4,5]
print(arr.length); // 6