Short intro about string functions in JavaScript

Learn about available JavaScript string functions.

String Properties

1.length

var str = "Jagathish";
str.length; //9  --> returns the length of the string

Functions

1. toUpperCase() –> returns the new string in uppercase format of source string

var str = "Jagathish";

var str2 = str.toUpperCase();

console.log(str);//Jagathish

console.log(str2);//JAGATHISH 

2.toLowerCase() –> returns the new string in lowercase format of source string

var str = "Jagathish";

var str2 = str.toLowerCase();

console.log(str);//Jagathish

console.log(str2);//jagathish

3.trim() –> returns a new string with removed white space from start and end of the string.

var str = "   Jagathish  ";

var trimmedStr = str.trim(); 

console.log(trimmedStr); //"Jagathish"

var str1 = "J  aga";
var trimmedStr1 = str1.trim();
console.log(trimmedStr1); //"J  aga"

var str2 = "J   .";
var trimmedStr2 = str2.trim();
console.log(trimmedStr2); //"J   ."

4.trimStart() –> returns a new string with removed white space from start of the string. trimLeft() is an alias of this method.

var str = "   Jagathish  ";

var trimmedStr = str.trimStart(); 

console.log(trimmedStr); //"Jagathish  "

5.trimEnd() –> returns a new string with removed white space at end of the string. trimRight() is an alias of this method.

var str = "   Jagathish  ";

var trimmedStr = str.trimEnd(); 

console.log(trimmedStr); //"   Jagathish"

5.charAt() –> returns the character at the given index.

var str = "Jagathish";

console.log( str.charAt() ); //the default index is 0 so "J"

str.charAt(1); //a

str.charAt(8); //h

str.charAt(100); //"" if max than str length returns empty string

str.charAt(-1); // for all negative values returns empty string

//no type conversion takes pace so the result is empty string
str.charAt("1");  //""

6.charCodeAt() –> returns the UTF-16 character code of the character at the given index. All rules of index in chatAt method is similar to charCodeAt.

// char code for a - 97, b =98 ,... z -122

// char code for A - 65 ... Z - 90

var str = "Jagathish";

str.charCodeAt(0); // 74

str.charCodeAt(1); // 97

7.concat(arguments) concate the arguments passed with the source string. It doesn’t change on source string.

var str = "JavaScript";

str.concat(' ', "Jeep", "."); // JavaScript Jeep.

Note: This method is not recommended , instead you can use normal concatenation using assignment operator.
Example

var str = "JavaScript".

var name = str + " " + "Jeep" +".";

8.includes(searchingString) returns whether searching String may be found in source string.

var str = "JavaScript Jeep";

str.includes("Jeep"); // true
str.includes("jeep"); // false --> case sensitive

// we can also specify the index to start search

var str = "Jeep";
str.includes("Jeep", 0);  // true
str.includes("Jeep", 1);  // false

9.endsWith(searchString) returns whether the source string ends with the searching string.

var str = "JavaScript Jeep";

str.endsWith("Jeep"); // true

str.endsWith("jeep"); // false

str.endsWith("Kepp"); // false

// we can also specify the endPosition(index+1) to which the test should run

var str = "Jeep";

str.endsWith("J");  //false

str.endsWith("J", 1) // true

10.startsWith(searchString) returns whether the source string starts with the searching string.

var str = "JavaScript Jeep";

str.startsWith("Java"); // true

str.startsWith("java"); // false

str.startsWith("Ava"); // false

// we can also specify the startPosition(index) to which the test should run

var str = "JAVASCRIPT"

str.startsWith("VA");  //false

str.startsWith("VA", 2) // true

str.startsWith("J", 1); // false --> because we are saying to start search from index 1 .

11.includes(searchString) determines whether search string found within source String

var str = "JavaScript Jeep";

str.includes("Java"); // true

str.includes("java"); // false

str.includes(""); // true

str.includes(); // false

we can also specify the index from which the search should start

str = "JavaScript";

str.include("Java", 0); //true

str.include("Java", 1); //false

12 . repeat(times) returns a new string containing the specified number of copies of the given string.Repeat value must be non-negative and less than infinity, otherwise range error will br thrown.

var str = "Jeep ";

var repeatedString = str.repeat(1); // "Jeep "

repeatedString = str.repeat(2); // "Jeep Jeep"

repeatedString = str.repeat(); // ""

repeatedString = str.repeat(0); // ""

13.indexOf(searchString) return the index of first occurrence of search string on the source string , if the search string not present in the source string then it returns -1.

var str = "Java Jeep JavaScript Jeep";

str.indexOf("Jeep"); // 5

str.indexOf('jeep'); // -1

// we can also specify the index from which the search should happen

str.indexOf("Java", 0); // 0
str.indexOf("Java", 1); // 10

14.lastIndexOf(searchString) return the index of last occurrence of search string on the source string , if the search string not present in the source string then it returns -1.

var str = "Java Jeep Java Jeep";

str.lastIndexOf("Jeep"); // 15

str.lastIndexOf('jeep'); // -1

15.match(regex) extract the result of matching a string against a regular expression.

// Extracting vowel character

var str = 'I love cooking.';

var regex = /[AEIOUaeiou]/gi;

var result = str.match(regex); //["I","o","e","o","o","i"]

16.search(regex) this method test whether the source string matches the regex provided. If the source string doesn’t match with the regex then return -1.

var str = "str";

var regex1 = /a-z/gi;

var regex2 = /[aeiou]/gi;

str.search(regex1); // 0 ('s' matches with the regex , where 's' is 
at 0th index)

str.search(regex2); // -1 (because there is no match) 

17.padStart(newStringLength) This method add the padding (space by default) to the source string at the beginning of the string ,so that the source string length is converted to the provided length.

var str = "Jeep";

str.padStart(5); // " Jeep"

str.padStart(10); // "      Jeep"

str.padStart(5, "*"); // "*Jeep"

str.padStart(10,"@"); // "@@@@@@Jeep"

// If the value is lower than the current string's length, the current string will be returned as is.

str.padStart(1); // "Jeep"

str.padStart(); // "Jeep"

str.padStart(-1); // "Jeep"

18.padEnd(newStringLength) This method add padding (space by default) to the source string at the end of the string , so that the source string length is converted to the provided length.

var str = "Jeep";

str.padEnd(5); // "Jeep "

str.padEnd(10); // "Jeep      "

str.padEnd(5, "*"); // "Jeep*"

str.padEnd(10,"@"); // "Jeep@@@@@@"

// If the value is lower than the current string's length, the current string will be returned as is.

str.padEnd(1); // "Jeep"

str.padEnd(); // "Jeep"

str.padEnd(-1); // "Jeep"

19.replace(regex, stringToReplace) this method replaces the string with stringToReplace which matches the pattern

var str = "I love dog. I love dog";

var regex =  /dog/g;

str.replace(regex, 'cat'); // I love cat. I love cat

20.splice(fromIndex, toIndex) extracts part of source string and returns it as a new string .

var str = "JavaScript Jeep";

str.slice(1); "avascript Jeep"

str.slice(10); " Jeep"

str.slice(11); "Jeep"

str.slice(11, 12); "J"

str.slice(11, 14); "Jee"

str.slice(0); "Javascript Jeep"

str.slice(); "Javascript Jeep"

21 . split(separator) this method split the string based on the separator.

var str = "Java Jeep";

str.split(""); // ['J', 'a', 'v', 'a' ," ", 'J', 'e','e', 'p']

str.split(" "); ["Java", "Jeep"]

str.split() // ["Java Jeep"]

------------------------------

// limiting number of split

var str = "this,is,a,test";

str.split(","); ["this", "is","a","test"]

str.split(",", 1); ["this"]

str.split(",", 2); ["this", "is"]

str.split(",",100); ["this", "is","a","test"]

22 . substring(startIndex, endIndex) returns the the string between the start and end indexes, or to the end of the string.

var str = "JavaScript Jeep";

str.substring(11); // "Jeep"

str.substring(11,12); // "J"

str.substring(); // "JavaScript Jeep"