Methods in Arrays – Part 3

Arrays topic in TypeScript is divided into following parts:

• Introduction to Arrays
• Array Objects
• Methods in Arrays – Part 1
• Methods in Arrays – Part 2
• Methods in Arrays – Part 3
• Multidimensional Arrays
• Arrays in functions

Below are the methods that are discussed in this section

reverse	shift	slice	some
sort	splice	toString	unshift

reverse

This method place the array elements in the reverse order.
Syntax

array.reverse();

Below is a sample code

var orgArr:number[] = [10,20,300];
console.log("Original array: " + orgArr);
var newArr:number[];
newArr = orgArr.reverse(); // assign the reversed array in a new array
console.log("Reversed Array: " + newArr); 
console.log("Original array is also modified: " + orgArr); // original array is also reversed

Below is the output of above code

shift

This method removes the first element of the array and returns that element, hence modifying the length of the array.
Syntax

array.shift();

Below is a sample code

var orgArr:number[] = [10,20,300];
console.log("Original array: " + orgArr);
console.log("Length of Original Array: " + orgArr.length);
var num:number = orgArr.shift();
console.log("First element: " + num);
console.log("Modified array: " + orgArr);
console.log("Length of Modified Array: " + orgArr.length);

Below is the output of above code

slice

This method returns a new array extracted from the original array based on the beginIndex and endIndex.
– beginIndex: The index from where you want to start the extraction. If the is negative, You can extract only those elements from the end of the array. Do not put endIndex if beginIndex is negative.
– endIndex: The index till where you want to continue the extraction. The element at this index is not included in the new array. This is optional.
Syntax

array.slice(beginIndex [, endIndex]);

Below is a sample code

var orgArr:number[] = [10,20,30,40,50,60];
console.log("Original array: " + orgArr);
console.log("array.slice(0): " + orgArr.slice(0));
console.log("array.slice(1): " + orgArr.slice(1));
console.log("array.slice(0,2): " + orgArr.slice(0,2));
console.log("array.slice(1,2): " + orgArr.slice(1,2));
console.log("array.slice(1,3): " + orgArr.slice(1,3));
console.log("array.slice(-1,2): " + orgArr.slice(-1,2));
console.log("array.slice(-1): " + orgArr.slice(-1));
console.log("array.slice(-2): " + orgArr.slice(-2));
console.log("array.slice(-1,4): " + orgArr.slice(-1,4));

Below is the output of above code

some

This method tests whether some array element passes the test implemented by the function. This method is different from every() method where all the array elements have to pass the test.
– Returns true even if one array element passes in the function test. It will return false if all the array element fails in the function test.
– functionName is the function that tests the array elements
Syntax

array.some(functionName);

Below is an example

// returns true
function test1(element, index, array) { 
    return (element >= 10); 
 } 
 var nums1:number[] = [1,2,3];
 var result1 = nums1.some(test1); 
 console.log("Test Value : " + result1);
 
 // returns false
 function test2(element, index, array) { 
    return (element >= 10); 
 } 
 var nums2:number[] = [10,5,30,2];
 var result2 = nums2.some(test2); 
 console.log("Test Value : " + result2 );

Below is the output of above code

sort

This method is used to sort the elements of the array based on a mentioned function. If the functionName is not specified, the array is sorted in lexicographically.
Syntax

array.sort(functionName);

Below is an example

var orgNumArr:number[] = [78,34,90,12,67];
console.log("Original Array: " + orgNumArr);
var newNumArr:number[] = orgNumArr.sort();
console.log("Sorted Array: " + newNumArr);
console.log("Original Array: " + orgNumArr);

var orgStrArr:string[] = ["red", "blue", "yellow", "green"];
console.log("\nOriginal Array: " + orgStrArr);
var newStrArr:string[] = orgStrArr.sort();
console.log("Sorted Array: " + newStrArr);
console.log("Original Array: " + orgStrArr);

var orgAlphaArr:string[] = ["red", "12blue", "yellow23", "7green","white"];
console.log("\nOriginal Array: " + orgAlphaArr);
var newAlphaArr:string[] = orgAlphaArr.sort();
console.log("Sorted Array: " + newAlphaArr);
console.log("Original Array: " + orgAlphaArr);

Below is the output of above code

splice

This method is used to add or remove array elements, hence modifying the array.
– index: index specifies the index from where we should start modifying the array.
– removeCount: this is used to mention the number of elements to be removed after the index. If you do not want to remove any element, specify 0.
– element1, element2,… : elements to be added in the array. This is optional. Mention the elements if you want to add the elements.
Syntax

array.splice(index, removeCount [element1, element2, ...]);

Below is an example

var orgArr:string[] = ["red", "blue", "yellow", "green","orange"];
console.log("Original Array: " + orgArr);
console.log("Original Length: " + orgArr.length);

console.log("\nAdding black at 3rd index and removing 0 elements.");
var element = orgArr.splice(3,0,"black");
console.log("Modified array: " + orgArr);
console.log("Removed element: " + element);
console.log("New Length: " + orgArr.length);

console.log("\nRemoving 1 element from 3rd index");
console.log("Array: " + orgArr);
var element = orgArr.splice(3,1);
console.log("Modified array: " + orgArr);
console.log("Removed element from 1st index: " + element);
console.log("New Length: " + orgArr.length);

console.log("\nRemove 2 elements from 2nd index then add white to 2nd index.");
console.log("Array: " + orgArr);
var element = orgArr.splice(2,2, "white");
console.log("Modified array: " + orgArr);
console.log("Removed element from 4th index: " + element);
console.log("New Length: " + orgArr.length);

Below is the output of above code

toString

Returns a string representing array and its elements.
Syntax

array.toString();

Below is an example

var orgArr:number[] = [10,20,30,40];
console.log("Original Array: " + orgArr);
console.log("typeOf of Original Array: " + typeof(orgArr));
var strArray = orgArr.toString();
console.log("String representation of array: " + strArray);
console.log("typeOf of Modified Array: " + typeof(strArray));
console.log("typeOf of Original Array: " + typeof(orgArr));

Below is the output of above code

unshift

This method will add elements in the beginning of the array and returns the new length of the array,
Syntax

array.unshift(element1 [,element2, element3,...]);

Below is an example

var orgArr:number[] = [10,20,30,40];
console.log("Original Array: " + orgArr);
console.log("Original Length: " + orgArr.length);
var newLength = orgArr.unshift(50,60);
console.log("Modified Array: " + orgArr);
console.log("New Length: " + newLength);

Below is the output of above code

Strings in TypeScript – Part 2

Strings in TypeScript is divided in three parts:

• Part 1
• Part 2. This is Part 2
• Part 3

This section has the details of following methods:

subString	subStr	split
slice	search	replace
match	localeCompare	lastIndexOf

lastIndexOf()

This method returns the last index of a specified value within a string. Search will start from the starting of the string. variable is the string in which we are searching for the value.
– searchString is the value which we are searching in the variable.
– fromIndex is an integer which specify the starting index for the search. It will return -1 if the string is not found.
Syntax

variable.lastIndexOf(searchString, [fromIndex])

Below is a sample code

var str1 = new String("This is a sample string sample");
console.log("Last Index of i: " + str1.lastIndexOf('i'));
console.log("Last Index of is: " + str1.lastIndexOf("is"));
console.log("Last Index of sample: " + str1.lastIndexOf("sample"));
console.log("Last Index of sample: " + str1.lastIndexOf("sample", 14));
console.log("Last Index of two: " + str1.lastIndexOf("two"));

Below is the output of above code

localeCompare()

This method will return an integer value after sorting two strings
Syntax

str1.localeCompare(str2);

– Returns 0 if str1 and str2 are equal.
– Returns 1 if str2 comes before str1 in the locale sort order.
– Returns -1 if str2 comes after str1 in locale sort order.

Below is an example

var str1 = new String("ab");
var str2 = new String("cd");    
var index1 = str1.localeCompare("ab");  
var index2 = str2.localeCompare("ab");  
var index3 = str1.localeCompare("cd"); 
console.log("Perfect Match: " + index1 );
console.log("Parameter value comes before the string value: " + index2 );
console.log("Parameter value comes after the string value: " + index3 );

Below is the output of above code

match()

This method searches a string for a match against a regular expression. This will return an array of all matches. Include g modifier to do a global search, that is in complete string. Otherwise it will return only the first match in the string. i is used to match without case-comparison. This method will return null if no match is found.
Syntax

variable.match(regexpre);

Below is an example

var str1 = new String("This is an example. ThiS IS good.");
console.log(str1.match(/is/g));
console.log(str1.match(/is/gi));

Below is the output of above code

replace

This method first finds a match between a regular expression and a string, then replaces the matched substring with another substring.
Syntax

variable.replace(regexp, substring);

Below is a sample code

var str1 = new String("I like to eat mangoes, but mangoes only come in summers. Mangoes are yellow in color.");
var result = str1.replace(/mangoes/gi,"apples");
console.log(result);

Below is the output of above code

search()

This method searches a substring, using a regular expression, within a string and returns the index.
If the regular expression is not inside the string, it will return -1.
Syntax

string.search(regexp);

Below is a sample code

var str1 = new String("I like to eat mangoes, but mangoes only come in summers. Mangoes are yellow in color.");
var index = str1.search(/mangoes/gi);
console.log("First index of mangoes: " + index);

Below is the output of above code

slice()

This method extracts a section of a string and returns a new string. You can remove characters from beginning as well as from the end of the string. Giving the value fromEnd is optional.
Syntax

string.slice(fromBeginning, [fromEnd]);

Below is an example

var str1 = new String("I like to eat mangoes, but mangoes only come in summers.");
console.log(str1.slice(4,-5));

Below is the output of above code

split

This will split a string into array based on a substring. This method returns an array.
– separator is the substring used to split a string.
– limitOfValues is an integer value that tells how many values to return.
Syntax

string.spli(separator, [limitOfValues])

Below is an example

var str1 = new String("red,orange,blue,black,yellow,green");
var colors = str1.split(',');
var i:number;
console.log("All color values");
for(i=0; i<colors.length; i++)
{
    console.log(colors[i]);
}
var colors1 = str1.split(',',3);
var i:number;
console.log("\nOnly 3 color values");
for(i=0; i&lt;colors1.length; i++)
{
    console.log(colors1[i]);
}

Below is the output of above code

substr()

This method will return a new string.
– startIndex represents the index from where we want to start extracting the substring.
– length is a number representing the number of characters we want to extract. This is optional.
Syntax

string.substr(startIndex, [length]);

Below is a an example

var str1 = new String("I like to eat mangoes, which are yellow in color");
console.log("Original String: " + str1);
console.log("(0): " + str1.substr(0));
console.log("(4): " + str1.substr(4));
console.log("(5,9): " + str1.substr(5,9));
console.log("(-2): " + str1.substr(-2));
console.log("(-5,4):" + str1.substr(-5,4));

Below is the output of above code

substring()

This method will return a new string between two indexes. It does not take negative values like we used in substr() method, hence we cannot start extraction from the end of the string.
– startIndex is the starting index from where the extraction should begin
– endIndex is the index where the extraction should end. This is optional.
Syntax

string.substring(startIndex,[endIndex]);

Below is an example

var str1 = new String("I like to eat mangoes, which are yellow in color");
console.log("Original String: " + str1);
console.log("(0): " + str1.substring(0));
console.log("(4): " + str1.substring(4));
console.log("(5,9): " + str1.substring(5,9));
console.log("(-2): " + str1.substring(-2));
console.log("(-5,4): " + str1.substring(-5,4));

Below is the output of the above code