Let's understand javascript String functions and how to use them.
String.charAt()
Returns a string representing the character at the given index.
const str = "Hello World";
str.charAt(0); // "H"
String.charCodeAt()
Returns a number representing the UTF-16 code unit value of the character at the given index.
const str = "Hello World";
str.charCodeAt(0); // 72
String.concat()
Returns a new string containing the concatenation of the given strings.
const str = "Hello";
const str2 = " World";
str.concat(str2); // "Hello World"
console.log(`${str}${str2}`); // "Hello World"
console.log(str + str2); // "Hello World"
String.endsWith()
Returns true if the string ends with the given string, otherwise false.
const str = "Hello World";
str.endsWith("World"); // true
String.includes()
Returns true if the string contains the given string, otherwise false.
const str = "Hello World";
str.includes("World"); // true
String.indexOf()
Returns the index within the string of the first occurrence of the specified value, or -1 if not found.
const str = "Hello World";
str.indexOf("World"); // 6
String.lastIndexOf()
Returns the index within the string of the last occurrence of the specified value, or -1 if not found.
const str = "Hello World";
str.lastIndexOf("World"); // 6
String.match()
Returns a list of matches of a regular expression against a string.
const str = "Hello World";
str.match(/[A-Z]/); // ["H"]
String.matchAll()
Returns a list of matches of a regular expression against a string.
const str = "Hello World";
str.matchAll(/[A-Z]/g); // ["H", "W"]
// OR
str.match(/[A-Z]/g); // ["H", "W"]
String.padEnd()
Returns a new string with some content padded to the end of the string.
const str = "Hello";
str.padEnd(15, "World"); // "HelloWorldWorld"
String.padStart()
Returns a new string with some content padded to the start of the string.
const str = "Hello";
str.padStart(15, "World"); // "WorldWorldWorldHello"
String.repeat()
Returns a new string which contains the specified number of copies of the string.
const str = "Hello";
str.repeat(3); // "HelloHelloHello"
String.replace()
Returns a new string with some or all matches of a regular expression replaced by a replacement string.
const str = "Hello World";
str.replace("l", "*"); // "He*lo World"
String.replaceAll()
Returns a new string with some or all matches of a regular expression replaced by a replacement string.
const str = "Hello World";
str.replaceAll("l", "*"); // "He**o Wor*d"
OR;
str.replace(/l/g, "*"); // "He**o Wor*d"
String.search()
Returns the index within the string of the first occurrence of the specified value, or -1 if not found.
const str = "Hello World 1";
const regex = /[^\D\s]/g; // Find digit
str.search(regex); // 12
String.slice()
Returns a new string containing the characters of the string from the given index to the end of the string.
const str = "Hello World";
str.slice(6); // "World"
String.split()
Returns an array of strings split at the given index.
const str = "Hello World";
str.split(" "); // ["Hello", "World"]
String.startsWith()
Returns true if the string starts with the given string, otherwise false.
const str = "Hello World";
str.startsWith("Hello"); // true
String.substring()
Returns a new string containing the characters of the string from the given index to the end of the string.
const str = "Hello World";
str.substring(1, 2); // "e"
NOTE: substring takes parameters as (from, to).
String.substr()
Returns a new string containing the characters of the string from the given index to the end of the string.
const str = "Hello World";
str.substr(1, 2); // "el"
NOTE: substr takes parameters as (from, length).
String.toLowerCase()
Returns a new string with all the uppercase characters converted to lowercase.
const str = "Hello World";
str.toLowerCase(); // "hello world"
String.toUpperCase()
Returns a new string with all the lowercase characters converted to uppercase.
const str = "Hello World";
str.toUpperCase(); // "HELLO WORLD"
String.toString()
Returns the string representation of the specified object.
const str = new String("Hello World");
console.log(str); // Object of String
str.toString(); // "Hello World"
String.trim()
Returns a new string with the leading and trailing whitespace removed.
const str = " Hello World ";
str.trim(); // "Hello World"
String.trimEnd()
Returns a new string with the trailing whitespace removed.
const str = " Hello World ";
str.trimEnd(); // " Hello World"
String.trimStart()
Returns a new string with the leading whitespace removed.
const str = " Hello World ";
str.trimStart(); // "Hello World "
Thank you for reading ๐
Got any questions or additional? please leave a comment.
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Top comments (3)
Using the string methods is not always crowned with success, especially when UTF-8 strings are used.
String.padStart()
Returns a new string with some content padded to the start of the string.
const str = "Hello";str.padStart(15, "World"); // "WorldWorldWorldHello"
Isn't there an extra "world" ?
I think it works like String.padEnd (the number 15 indicates the final length after characters are added, which is not the case here, it has a length of 20).
Thank you for this cheat sheet, I love it ๐๐
does not have a methods .capitalize() how in python?,