String Object Method In TypeScript: Part 1

Introduction

 

The String object is used to manage a series of characters. The String object contains complete information about strings. In TypeScript, String objects are created with "new String()".

 

In this article, I am describing the TypeScript charAt and charCodeAt string methods.

 

chatAt() Method

 

In TypeScript, the charAt() method returns the character at the specified position in the string. Characters in a string proceed (are indexed) from left to right. The position of the first character is 0 and the position of the last character in a string is string.length - 1.

 

Syntax

string.charAt(position)

position: is a required parameter; represents the position of the character.

 

Function

 

A sample use of charAt is:

charAt(str: string) {
 var position = str.charAt(0);
 var span = document.createElement("span");
 span.innerText = "charAt Method \n Display the first character of a string-> " + position + "\n";
 document.body.appendChild(span);
}

charCodeAt() Method

 

In TypeScript the charCodeAt() method returns a number that represents the Unicode value of the character at the given position.

 

Syntax

string.charCodeAt(position)

position: is a required parameter; the position value is between 0 and the position of the last character, which is 1 less than the length of the string. The default position is 0.

 

Function

 

A sample use of charCodeAt is:

charCodeAt(str: string) {
 var unicode = str.charCodeAt(str.length - 1);
 var span = document.createElement("span");
 span.style.color = "green";
 span.innerText = "charCodeAt Method \n Display the unicode of the last character in a string-> " + unicode + "\n";
 document.body.appendChild(span);
}

The following example shows how to use charAt and charCodeAt methods in TypeScript. In this example, we get a string from the user. The charAt() method returns the character at the specified position and the charCodeAt() method returns a Unicode character at a specified index.

 

Complete Program

 

chatAt_charCodeAt.ts

class charAt_charCodeAt {
 charAt(str: string) {
  var position = str.charAt(0);
  var span = document.createElement("span");
  span.innerText = "charAt Method \n Display the first character of a string-> " + position + "\n";
  document.body.appendChild(span);
 }
 charCodeAt(str: string) {
  var unicode = str.charCodeAt(str.length - 1);
  var span = document.createElement("span");
  span.style.color = "green";
  span.innerText = "charCodeAt Method \n Display the unicode of the last character in a string-> " + unicode + "\n";
  document.body.appendChild(span);
 }
}
window.onload = () => {
 var obj = new charAt_charCodeAt();
 var str = prompt("Please enter a string");
 obj.charAt(str);
 obj.charCodeAt(str);
};

chatAt_charCodeAt_MethodDemo.htm

< !DOCTYPE html >
 <
 html lang = "en"
xmlns = "http://www.w3.org/1999/xhtml" >
 <
 head >
 <
 meta charset = "utf-8" / >
 <
 title > TypeScript HTML App < /title>
 <
 link rel = "stylesheet"
href = "app.css"
type = "text/css" / >
 <
 script src = "charAt_charCodeAt.js" > < /script>
 <
 /head>
 <
 body >
 <
 h3 > charAt() and charCodeAt() String Object Method In TypeScript < /h3>
 <
 div id = "content" / >
 <
 /body>
 <
 /html>

chatAt_charCodeAt.js

var charAt_charCodeAt = (function() {
 function charAt_charCodeAt() {}
 charAt_charCodeAt.prototype.charAt = function(str) {
  var position = str.charAt(0);
  var span = document.createElement("span");
  span.innerText = "charAt Method \n Display the first character of a string-> " + position + "\n";
  document.body.appendChild(span);
 };
 charAt_charCodeAt.prototype.charCodeAt = function(str) {
  var unicode = str.charCodeAt(str.length - 1);
  var span = document.createElement("span");
  span.style.color = "green";
  span.innerText = "charCodeAt Method \n Display the unicode of the last character in a string-> " + unicode + "\n";
  document.body.appendChild(span);
 };
 return charAt_charCodeAt;
})();
window.onload = function() {
 var obj = new charAt_charCodeAt();
 var str = prompt("Please enter a string");
 obj.charAt(str);
 obj.charCodeAt(str);
};

Output 1

 

Enter a string and click on "Ok":

 

 

Output 2