1. Simple String Replacement
Replace the first occurrence of a substring.
let str = "Hello world!";
let result = str.replace("world", "JavaScript");
// Output: "Hello JavaScript!"
2. Global String Replacement
Replace all occurrences of a substring, use the global (g) flag with regular expression.
let str = "Hello world, world!";
let result = str.replace(/world/g, "JavaScript");
// Output: "Hello JavaScript, JavaScript!"
3. Case-insensitive Replacement
You can make the replacement case-insensitive using the i flag.
let str = "Hello World, World!";
let result = str.replace(/world/gi, "JavaScript")
// Output: "Hello JavaScript, JavaScript!"
4. Replace Whole Words (Word Boundary)
Replace only whole words using \b word boundary.
let str = "This is a test word, test.";
let result = str.replace(/\btest\b/, "success");
// Output: "This is a success word, test."
Replace all occurrences of the whole word, use the global flag.
let str = "This is a test word, test.";
let result = str.replace(/\btest\b/g, "success");
// Output: "This is a success word, success."
5. Using a Function for Replacement
You can pass a function to replace() that dynamically generates the replacement string.
let str = "The price is $10";
let result = str.replace(/\$\d+/g, (match) => {
return `$${parseInt(match.substring(1)) * 2}`
});
// Output: "The price is $20"
6. Capturing Groups with Replacement
Using regular expressions, you can capture parts of the match and reuse them in the replacement string.
let str = "John Smith";
let result = str.replace(/(\w+)\s(\w+)/, "$2, $1");
// Output: "Smith, John"
7. Escaping Special Characters
If you need to replace special characters like . or *, you need to escape them in the regular expression.
let str = "Price: 5.99";
let result = str.replace(/\./, ",");
// Output: "Price: 5,99"
8. Replacing Non-ASCII Characters
To replace characters that aren't in the ASCII range, you can use Unicode properties.
let str = "Héllo Wörld";
let result = str.replace(/[^\x00-\x7F]/g, "");
// Output: "Hllo Wrld"
9. Replacing Digits
You can replace digits (or groups of digits) using regular expressions.
let str = "Contact: 123-456-7890";
let result = str.replace(/\d{3}/g, "***");
// Output: "Contact: ***-***-***0"
10. Replacing Special Characters using Unicode
You can also use Unicode escape sequences to replace special characters.
let str = "I love ☕!";
let result = str.replace(/\u2615/g, "coffee");
// Output: "I love coffee!"
11. Replace Words using Lookbehind and Lookahead assertion
Replace only whole words while preserving the surrounding whitespace.
let str = "This is a test word, test.";
let result = str.replace(/(?<=\s|^)test(?=\s|$)/, "success");
// Output: "This is a success word, test."
Replace all occurrences of the whole word, use the global flag.
let str = "This is a test word, test.";
let result = str.replace(/(?<=\s|^)test(?=\s|$)/g, "success");
// Output: "This is a success word, test."
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