Cara menggunakan replace unicode characters php

Everyone working with JavaScript will have to deal with strings at one point or other. Sometimes, you will just have to store a string inside another variable and then pass it over. Other times, you will have to inspect it and see if it contains a particular substring.

However, things are not always this easy. There will be times when you will not be looking for a particular substring but a set of substrings which follow a certain pattern.

Let's say you have to replace all occurrences of "Apples" in a string with "apples". You could simply use

"I ate Apples".replace("Apples", "apples");

Now let's say you have to replace "appLes" with "apples" as well. Similarly, "appLES" should become "apples" too. Basically, all case variations of "Apple" need to be changed to "apple". Passing simple strings as an argument will no longer be practical or efficient in such cases.

This is where regular expressions come in—you could simply use the case-insensitive flag

"I ate Apples".replace("Apples", "apples");

Just like the case-insensitive flag, regular expressions offer a lot of other features which will be covered in this tutorial.

Using Regular Expressions in JavaScript

You have to use a slightly different syntax to indicate a regular expression inside different

"I ate Apples".replace("Apples", "apples");

Going back to the previous example, here is what the

"I ate Apples".replace("Apples", "apples");

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"I ate Apples".replace("Apples", "apples");

2

// I ate apples

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4

"I ate Apples".replace(/Apples/i, "apples");

5

// I ate apples

6

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

As you can see, the regular expression worked in both cases. We will now learn more about flags and special characters that make up the pattern inside a regular expression.

Backslash in Regular Expressions

You can turn normal characters into special characters by adding a backslash before them. Similarly, you can turn special characters into normal characters by adding a backslash before them.

For example,

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

Digit characters include 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. When you use

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

The following example should make things clear.

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"I ate Apples".replace("Apples", "apples");

// I ate apples

"I ate Apples".replace("Apples", "apples");

// I ate apples

You should note that only the first matched character is replaced in the third case. You can also use flags to replace all the matches. We will learn about such flags later.

Just like

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

1. You can use

   "I ate Apples".replace("Apples", "apples");
   

   38 to match any "word" character in a string. Here, word character refers to A-Z, a-z, 0-9, and _. So, basically, it will match all digits, all lowercase and uppercase alphabets, and the underscore.
2. You can use

   "I ate Apples".replace("Apples", "apples");
   

   39 to match any non-word character in a string. It will match characters like %, $, #, ₹, etc.
3. You can use

   "I ate Apples".replace("Apples", "apples");
   

   40 to match a single white space character, which includes space, tab, form feed, and line feed. Similarly, you can use

   "I ate Apples".replace("Apples", "apples");
   

   41 to match all other characters besides white space.
4. You can also look for a specific white space character using

   "I ate Apples".replace("Apples", "apples");
   

   42,

   "I ate Apples".replace("Apples", "apples");
   

   43,

   "I ate Apples".replace("Apples", "apples");
   

   44,

   "I ate Apples".replace("Apples", "apples");
   

   45, and

   "I ate Apples".replace("Apples", "apples");
   

   46, which stand for form feed, line feed, carriage return, horizontal tab, and vertical tab.

Sometimes, you will face situations where you need to replace a word with its substitute, but only if it is not part of a larger word. For example, consider the following sentence:

"A lot of pineapple images were posted on the app".

In this case, we want to replace the word "app" with "board". However, using a simple regular expression pattern will turn "apple" into "boardle", and the final sentence would become:

"A lot of pineboardle images were posted on the app".

In such cases, you can use another special character sequence: 

"I ate Apples".replace("Apples", "apples");

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// I ate apples

2

// I ate apples

3

4

// I ate apples

5

3

Similarly, you can use

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

Matching a Pattern "n" Number of Times

You can use

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

You can use

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

In a similar manner, you can use

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

Sometimes, you only want to match a specific number of occurrences of a given pattern. In such cases, you should use the

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

You can use

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

You can also use

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

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3

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3

6

"I ate Apples".replace("Apples", "apples");

4

"I ate Apples".replace("Apples", "apples");

4

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

4

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace(/Apples/i, "apples");

"I ate Apples".replace(/Apples/i, "apples");

"I ate Apples".replace(/Apples/i, "apples");

"I ate Apples".replace(/Apples/i, "apples");

"I ate Apples".replace(/Apples/i, "apples");

"I ate Apples".replace(/Apples/i, "apples");

Using Parentheses to Remember Matches

So far, we have only replaced patterns with a constant string. For example, in the previous section, the replacement we used was always "Add". Sometimes, you will have to look for a pattern match inside the given string and then replace it with a part of the pattern.

Let's say you have to find a word with five or more letters in a string and then add an "s" at the end of the word. In such cases, you will not be able to use a constant string value as a replacement as the final value depends on the matching pattern itself.

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"I ate Apples".replace(/Apples/i, "apples");

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"I ate Apples".replace(/Apples/i, "apples");

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5

This was a simple example, but you can use the same technique to keep more than one matching pattern in memory. The number of sub-patterns in the full match will be determined by the number of parentheses used.

Inside the replacement string, the first sub-match will be identified using

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

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5

2

5

Using Flags With Regular Expressions

As I mentioned in the introduction, one more important feature of regular expressions is the use of special flags to modify how a search is performed. The flags are optional, but you can use them to do things like making a search global or case-insensitive.

These are the four commonly used flags to change how JavaScript searches or replaces a string.

• "I ate Apples".replace("Apples", "apples");
  

  64: This flag will perform a global search instead of stopping after the first match.

• "I ate Apples".replace("Apples", "apples");
  

  27: This flag will perform a search without checking for an exact case match. For instance, Apple, aPPLe, and apPLE are all treated the same during case-insensitive searches.

• "I ate Apples".replace("Apples", "apples");
  

  66: This flag will perform a multi-line search.

• "I ate Apples".replace("Apples", "apples");
  

  67: This flag will look for a match in the index indicated by the

  "I ate Apples".replace("Apples", "apples");
  

  68 property.

Here are some examples of regular expressions used with flags:

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// I ate apples

2

// I ate apples

3

4

// I ate apples

5

// I ate apples

6

"I ate Apples".replace("Apples", "apples");

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"I ate Apples".replace("Apples", "apples");

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"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

6

"I ate Apples".replace("Apples", "apples");

// I ate apples

"I ate Apples".replace(/Apples/i, "apples");

"I ate Apples".replace(/Apples/i, "apples");

"I ate Apples".replace(/Apples/i, "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

// I ate apples

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

"I ate Apples".replace("Apples", "apples");

Final Thoughts

The purpose of this tutorial was to introduce you to regular expressions in JavaScript and their importance. We began with the basics and then covered backslash and other special characters. We also learned how to check for a repeating pattern in a string and how to remember partial matches in a pattern in order to use them later.

Finally, we learned about commonly used flags which make regular expressions even more powerful. You can learn more about regular expressions in this article on MDN.