The .charAt(index) method returns the character at the specified index in a string.
let str = "Hello, World!";
let char = str.charAt(0);
console.log(char); // Output: "H"The .charCodeAt(index) method returns the Unicode of the character at the specified index in a string.
let str = "Hello, World!";
let charCode = str.charCodeAt(0);
console.log(charCode); // Output: 72
Example: Alphabet Position to Number Positon
function position(letter){
letter = letter.toLowerCase();
let positionABC = letter.charCodeAt(0) - 96;
return positionABC;
}The .concat(string1, string2, ...) method concatenates one or more strings to the calling string and returns a new string.
let str = "Hello";
let newStr = str.concat(", ", "World!");
console.log(newStr); // Output: "Hello, World!"The .endsWith(searchString, length) method returns a boolean indicating whether a string ends with the specified string at the specified position.
let str = "Hello, World!";
let result = str.endsWith("World!");
console.log(result); // Output: trueThe .includes(searchString, position) method returns a boolean indicating whether a string contains the specified string at the specified position.
let str = "Hello, World!";
let result = str.includes("World");
console.log(result); // Output: trueThe .indexOf(searchValue, start) method returns the first index at which a given element can be found in the array, or -1 if it is not present
let str = "Hello World!";
let index = str.indexOf("o");
console.log(index); // 4The .lastIndexOf(searchValue, start) method returns the last index at which a given element can be found in the array, or -1 if it is not present
let str = "Hello World! Hello World!";
let index = str.lastIndexOf("o");
console.log(index); // 15The .length property returns the number of characters in a string.
let str = "Hello, World!";
let strLength = str.length;
console.log(strLength); // Output: 13The .localeCompare(compareString) method compares the calling string to a specified string in the current locale and returns a number indicating whether the calling string is less than, equal to, or greater than the specified string.
let str1 = "Hello";
let str2 = "world";
let comparison = str1.localeCompare(str2);
console.log(comparison); // Output: -1 (str1 is less than str2 in lexicographic order)The .match(searchValue) method searches a string for a match against a regular expression, and returns the matches as an Array object.
let str = "Hello World! Hello World!";
let matches = str.match(/Hello/g);
console.log(matches); // ["Hello", "Hello"]The .repeat(count) method returns a new string with the specified number of copies of the original string.
function repeatStr (num, str) {
return str.repeat(num);
}
//Example:
let str = "Hello";
let newStr = str.repeat(3);
console.log(newStr); // Output: "HelloHelloHello"
//Example 2:
function repeatWord(num, str) {
let repeatedString = repeatStr(num, str);
console.log(repeatedString);
}
repeatWord(2, "Hello"); // "HelloHello"The .replace(searchValue, newValue) method replaces a specified value with another value in a string
let str = "Hello World!";
let newStr = str.replace("World", "Universe");
console.log(newStr); // "Hello Universe!"
Example:
Example 1: Replace string with any Word
function replaceWords(str, replaceWord) {
return str.replace(/\S+/g, replaceWord); // \S+ matches sequences of one or more non-whitespace characters, so replace every word with replaceWord
}
//Example 2: Ceaser Cypher Shift Positive or Negative
function caesar(str, shift) { // shift is the cypher # shifted positive or negative
const alphabet = 26; // the number of letters in the alphabet
shift = ((shift % alphabet) + alphabet) % alphabet; // ensure the shift value is always positive and less than alphabet
return str.replace(/[a-zA-Z]/g, (char) => { // use a regular expression to match all uppercase and lowercase letters
let code = char.charCodeAt(0) + shift; // get the unicode value of the current letter
if ((code > 90 && code < 97) || code > 122) { // check if the code is outside the range of uppercase or lowercase letters
code -= alphabet; // if it is, wrap it around the alphabet by subtracting alphabet
}
return String.fromCharCode(code); // return the shifted letter as a string
});
}
console.log(caesar("HELLO", 3)); // returns "KHOOR"The .search(searchValue) method searches a string for a specified value and returns the position of the match.
let str = "Hello World!";
let index = str.search("World");
console.log(index); // 6The .slice(start, end) method returns a subset of a string between a start and end index (if you provide only one number, it will start from that index to the end of the string)
let str = "Hello World!";
let slc = str.slice(2, 8);
console.log(slc); // "llo Wo"The .split(separator) method splits a string into an array of substrings, using the specified separator.
let str = "Hello, World!";
let strArray = str.split(",");
console.log(strArray); // Output: ["Hello", " World!"]
//Example: Remove spaces
let str = "Hello World";
let newStr = str.split(' ').split('');
console.log(newStr); // "HelloWorld"The .startsWith(searchString, position) method returns a boolean indicating whether a string starts with the specified string at the specified position.
let str = "Hello, World!";
let result = str.startsWith("Hello");
console.log(result); // Output: trueThe .substr(start, length) method returns a subset of a string starting from a specified index and with a specified length
let str = "Hello World!";
let sub = str.substr(2, 6);
console.log(sub); // "llo Wo"The substring() method returns a subset of a string between a start and end index
let str = "Hello World!";
let sub = str.substring(2, 8);
console.log(sub); // "llo WThe .toLowerCase() method returns the calling string value converted to lowercase.
let str = "Hello, World!";
let newStr = str.toLowerCase();
console.log(newStr); // Output: "hello, world!"The .toString() method returns the value of a string object
let str = new String("Hello World!");
console.log(str.toString());The .toUpperCase() method returns the calling string value converted to uppercase.
let str = "Hello, World!";
let newStr = str.toUpperCase();
console.log(newStr); // Output: "HELLO, WORLD!"The .trim() method removes whitespace from the beginning and end of a string.
let str = " Hello, World! ";
let newStr = str.trim();
console.log(newStr); // Output: "Hello, World!"Determines whether the passed value is a finite number, returns a Boolean.
isFinite(Infinity)Determines whether the passed value is an integer, returns a Boolean.
isInteger(3.14) // returns falseDetermines whether the passed value is NaN (Not a Number), returns a Boolean.
isNaN(NaN) // returns true.Determines whether the passed value is a safe integer, returns a Boolean. Safe integers are integers that can be exactly represented in JavaScript.
isSafeInteger(9007199254740990) // returns false.Parses a string argument and returns a floating-point
parseFloat("3.14") // returns 3.14.Parses a string argument and returns an integer.
parseInt("11", 2) // returns 3.Returns a string representing the number in exponential notation. The fractionDigits parameter is optional and specifies the number of digits after the decimal point.
(3.14).toExponential(1) // returns "3.1e+0".Returns a string representing the number with a specified number of decimal places.
(3.14159).toFixed(2) // returns "3.14".Returns a string representing the number using the current locale.
(3.14).toLocaleString // might return "3,14" in some locales.Returns a string representing the number with a specified number of significant digits.
(3.14159).toPrecision(2) // returns "3.1".eturns a string representing the The radix parameter is optional and specifies the base of the returned string.
(11).toString(2) // returns "1011".Returns the primitive value of a Number object.
(new Number(3.14)).valueOf // returns 3.14.