Which methods can be used to convert all characters in a string into a?
The Show
Example
Syntax of String upper()The syntax of string.upper() upper() Parameters
upper() Return Value
If no lowercase characters exist, it returns the original string. Example 1: Convert a string to uppercase
Output THIS SHOULD BE UPPERCASE! TH!S SH0ULD B3 UPP3RCAS3! Example 2: How upper() is used in a program?
Output The strings are same. Note: If you want to convert to lowercase string, use lower(). You can also use swapcase() to swap between lowercase to uppercase. Now that we've looked at the very basics of strings, let's move up a gear and start thinking about what useful operations we can do on strings with built-in methods, such as finding the length of a text string, joining and splitting strings, substituting one character in a string for another, and more. Prerequisites:Basic computer literacy, a basic understanding of HTML and CSS, an understanding of what JavaScript is.Objective:To understand that strings are objects, and learn how to use some of the basic methods available on those objects to manipulate strings.Strings as objectsMost things are objects in JavaScript. When you create a string, for example by using
your variable becomes a string object instance, and as a result has a large number of properties and methods available to it. You can see this if you go to the 7 object page and look down the list on the side of the page!Now, before your brain starts melting, don't worry! You really don't need to know about most of these early on in your learning journey. But there are a few that you'll potentially use quite often that we'll look at here. Let's enter some examples into the browser developer console. Finding the length of a stringThis is easy — you use the 8 property. Try entering the following lines:
This should return the number 7, because "mozilla" is 7 characters long. This is useful for many reasons; for example, you might want to find the lengths of a series of names so you can display them in order of length, or let a user know that a username they have entered into a form field is too long if it is over a certain length. Retrieving a specific string characterOn a related note, you can return any character inside a string by using square bracket notation — this means you include square brackets ( 9) on the end of your variable name. Inside the square brackets, you include the number of the character you want to return, so for example to retrieve the first letter you'd do this:
Remember: computers count from 0, not 1! To retrieve the last character of any string, we could use the following line, combining this technique with the 8 property we looked at above:
The length of the string "mozilla" is 7, but because the count starts at 0, the last character's position is 6; using 1 gets us the last character.Testing if a string contains a substringSometimes you'll want to find if a smaller string is present inside a larger one (we generally say if a substring is present inside a string). This can be done using the 2 method, which takes a single parameter — the substring you want to search for.It returns 3 if the string contains the substring, and 4 otherwise.
Often you'll want to know if a string starts or ends with a particular substring. This is a common enough need that there are two special methods for this: 5 and 6:
Finding the position of a substring in a stringYou can find the position of a substring inside a larger string using the 7 method. This method takes two parameters – the substring that you want to search for, and an optional parameter that specifies the starting point of the search.If the string contains the substring, 7 returns the index of the first occurrence of the substring. If the string does not contain the substring, 7 returns 0.
Starting at 1, if you count the number of characters (including the whitespace) from the beginning of the string, the first occurrence of the substring 2 is at index 3.
This, on the other hand, returns 0 because the character 5 is not present in the string.So now that you know how to find the first occurrence of a substring, how do you go about finding subsequent occurrences? You can do that by passing in a value that's greater than the index of the previous occurrence as the second parameter to the method.
Here we're telling the method to search for the substring 2 starting at index 7 ( 8), and it returns the index 9.Extracting a substring from a stringYou can extract a substring from a string using the 0 method. You pass it:
For example: 0The character at index 1 is 2, and the character at index 4 is 3. So we extract all characters starting at 2 and ending just before 3, giving us 6.If you know that you want to extract all of the remaining characters in a string after a certain character, you don't have to include the second parameter. Instead, you only need to include the character position from where you want to extract the remaining characters in a string. Try the following: 1This returns 7 — this is because the character position of 2 is the letter 8, and because you didn't include a second parameter, the substring that was returned was all of the remaining characters in the string.Note: 0 has other options too; study the 0 page to see what else you can find out.Changing caseThe string methods 1 and 2 take a string and convert all the characters to lower- or uppercase, respectively. This can be useful for example if you want to normalize all user-entered data before storing it in a database.Let's try entering the following lines to see what happens: 2Updating parts of a stringYou can replace one substring inside a string with another substring using the 3 method.In this example, we're providing two parameters — the string we want to replace, and the string we want to replace it with: 3Note that 3, like many string methods, doesn't change the string it was called on, but returns a new string. If you want to update the original 5 variable, you would have to do something like this: 4Also note that we now have to declare 5 using 7, not 8, because we are reassigning it.Be aware that 3 in this form only changes the first occurrence of the substring. If you want to change all occurrences, you can use 0: 5Active learning examplesIn this section, we'll get you to try your hand at writing some string manipulation code. In each exercise below, we have an array of strings, and a loop that processes each value in the array and displays it in a bulleted list. You don't need to understand arrays or loops right now — these will be explained in future articles. All you need to do in each case is write the code that will output the strings in the format that we want them in. Each example comes with a "Reset" button, which you can use to reset the code if you make a mistake and can't get it working again, and a "Show solution" button you can press to see a potential answer if you get really stuck. Filtering greeting messagesIn the first exercise, we'll start you off simple — we have an array of greeting card messages, but we want to sort them to list just the Christmas messages. We want you to fill in a conditional test inside the 1 structure to test each string and only print it in the list if it is a Christmas message.Think about how you could test whether the message in each case is a Christmas message. What string is present in all of those messages, and what method could you use to test whether it is present? 6 7 8Fixing capitalizationIn this exercise, we have the names of cities in the United Kingdom, but the capitalization is all messed up. We want you to change them so that they are all lowercase, except for a capital first letter. A good way to do this is to:
Note: A hint — the parameters of the string methods don't have to be string literals; they can also be variables, or even variables with a method being invoked on them. 9 7 1Making new strings from old partsIn this last exercise, the array contains a bunch of strings containing information about train stations in the North of England. The strings are data items that contain the three-letter station code, followed by some machine-readable data, followed by a semicolon, followed by the human-readable station name. For example: 2We want to extract the station code and name, and put them together in a string with the following structure: 3We'd recommend doing it like this:
4 7 6Test your skills!You've reached the end of this article, but can you remember the most important information? You can find some further tests to verify that you've retained this information before you move on — see Test your skills: Strings. ConclusionYou can't escape the fact that being able to handle words and sentences in programming is very important — particularly in JavaScript, as websites are all about communicating with people. This article has given you the basics that you need to know about manipulating strings for now. This should serve you well as you go into more complex topics in the future. Next, we're going to look at the last major type of data we need to focus on in the short term — arrays. Which of these methods can be used to convert all characters in a string into a character array *?char[] toCharArray() : This method converts string to character array.
Which methods can be used to convert all characters in a string into a character?We can convert String to char in java using charAt() method of String class. The charAt() method returns a single character only. To get all characters, you can use loop.
How to convert a char * to string in C++?There are three ways to convert char* into string in C++.. Using the “=” operator.. Using the string constructor.. Using the assign function.. How to convert character into string?valueOf(char c) This is the most efficient method to convert char to string. You should always use this method and this is the recommended way to convert character to string in java program.
|