Js String & Array Methods

String & Array Methods

String Methods

indexOf()

The indexOf() method returns the index of(the position of) the first occurrence of a specified text in a string.

var str = "I love sololearn and I also love programming";
var pos = str.indexOf("love");

String (str):

Result (pos):

| NOTICE |
1) string methods help you to work with Strings.
2) javascript counts position from Zero. 0 is the first position in a string, 1 is the second , 2 is the third ...
3) Both indexOf() and lastIndexOf() methods return -1 if the text ìs not found.

lastIndexOf()

The lastIndexOf() method returns the index of the Last occurrence of a specified text in a string.

var str = "I love sololearn and I also love programming";
var pos = str.lastIndexOf("love");

String (str):

Result (pos):

search()

The search() method searches a string for a specified value and returns the position of the match:

var str = "javascript is very Powerful";
var pos = str.search("is");

String (str):

Result (pos):

| NOTICE |
1) The Two methods, indexOf() and search() , are equal.they return same value.
2)But search() method can take more powerful search values.

Extracting String Parts

There are 3 methods

slice(start , end)
substring(start , end)
substr(start , length)

slice()

The slice() method extracts a part of a string and returns the extracted part in a new string.
string.slice( begin , end );

var str = "Javascript is easy to learn";
var x = str.slice(14);
var y = str.slice(0 , 10);

string (str):

with 1 parameter (x):

with 2 parameters (y):

If a Parameter is negative,the position is counted from the end of the string.
This example slices out the portion of a string from position -9 to position -5.

var str = "I Love Sololearn";
var res1 = str.slice(-9 , -5);
var res2 = str.slice(-14);

res1 result :

res2 result :

substring()

substring() method is similar to slice().
The difference is that substring() cannot accept Negative Indexes.

var str = "Javascript is easy to learn";
var res = str.substring(0 , 18);
var n_res = str.substring(-14);

String (str):

Result (res):

Negative Result (n_res):

substr()

substr() is similar to slice().
The difference is that the second parameter specifies the Length of the extracted part.

var str = "Hello World!";
var fir_ex = str.substr(6 , 5);
var sec_ex = str.substr(0 , 4);

String (str):

Result (fir_ex):

Result (sec_ex):

| NOTICE |
1) if the first parameter is negative , position counts from the end of the string.
2)second parameter can not be negative , because it defines the length.
3)if you omit the second parameter , substr() will slice out the rest of the string.

replace()

The replace() method replaces a specified value with another value in string.
This method can also take a regular expression as the search value.

var str = "I love you";
var x = str.replace("you" , "Sololearn");
var y = str.replace(/you/g , "Programming");

String (str):

First Method (x):

Second Method (y):

toUpperCase()

A string is converted to upper case with toUpperCase().

var str = "you can do it!";
var x = str.toUpperCase();

Before (str):

After (x):

toLowerCase()

A string is converted to lower case with toLowerCase().

var str = "YES, I CAN DO IT!";
var x = str.toLowerCase();

Before (str):

After (x):

concat()

concat() joins two or more strings:

var x = "Solo";
var y = "Learn";
var res = x.concat(" " , y);

part1 (x):

part2 (y):

Result (res):

The concat() method can be use instead of the Plus Operator.These two lines do the same.

var x = "Hello" + " " + "Friends";
var y = "Hello".concat(" " , "Friends");

With Plus (x):

With Cancat (y):

| NOTICE |
All string methods return a new string . they don't modify the original string.
Formally said : strings are immutable : strings cannot be changed, only replaced.

Extracting String Characters

There are 3 safe methods

charAt(position)
charCodeAt(position)
formCharCode(unicode)

charAt()

The charAt() method returns the character at a specified index(position) in a string.

var str = "Sololearn";
var w = str.charAt("5");
var x = str.charAt("6");
var y = str.charAt("7");
var z = w + x + y;

part 1 (w):

part 2 (x):

part 3 (y):

Result (z):

charCodeAt()

The charCodeAt() method returns the unicode of the character at a specified index in a string.

var str = "Hello World!";
var x = str.charCodeAt("7");
var y = str.charCodeAt("9");
var z = str.charCodeAt("10");

First (x):

Second (y):

Third (z):

fromCharCode()

The fromCharCode() method converts unicode values into characters.

var str = "Hello World!";
var w = String.fromCharCode(111);
var x = String.fromCharCode(108);
var y = String.fromCharCode(100);
var z = String.fromCharCode(111 , 108 , 100);

First (w):

Second (x):

Third (y):

Result (z):

Accessing a strng is an Array is Unsafe

you might have seen this code like this . accessing a string as an array.

var str = "Javascript";
var x = str[0];

String (str):

Result (x):

| NOTICE |
This is unsafe and unpredictable:
it does not work in all browsers.
it makes strings look like array.(but they are not)
str[0] = "J" does not give an error.(but does not work)

Split() - converting string to an array

str.split(","); //split on commas
str.split(" "); //split on spaces
str.split("|"); //split on pipe

var str = "html , css , javascript";
var arr = str.split(" , ");
var arr1 = arr[1];
var arr2 = arr.length;
typeof str;

typeof string :

First Result (arr):

Second Result (arr1):

Third Result (arr2):

trim()

The trim() method returns a string stripped of Whitespace from both ends.
This method does not change the value of the string itself.

var str = "___Hello World!___";
var x = str.length;
var y = str.trim();
var z = y.length;

Before Length (x):

Triming (y):

After Length (z):

trimLeft()

The trimLeft() method returns a string stripped of whitespace from the left end of the string.

var str = "_____Welcome to Sololearn______";
var x = str.length;
var y = str.trimLeft();
var z = y.length;

Before length(x):

Trimning Left (y):

After length (z):

trimRight()

The trimRight() method returns a string stripped of whitespace from the end of the string.

var str = "_____Welcome to Sololearn______";
var x = str.length;
var y = str.trimRight();
var z = y.length;

Before length(x):

Trimning Right (y):

After length (z):

match()

1)The match() method searches a string for a match against a regular expression, and returns the Matches,as an array object.
2)if you not include g modifier will returns only the first match in the string.
3)This method returns null if not match is found.

var x =
"The rain in SPAIN stays Mainly in the plain";
var y = x.match(/ain/g); //case-sensitive
var z = x.match(/ain/gi); //case-insensitive

String (x):

Sensitive Match (y):

Insensitive Match (z):

repeat()

The repeat() method returns a new string with a specified number of copies of the string it was called on.

var x = "Welcome to Sololearn ";
var y = x.repeat(2);
var z = x.repeat(7);

String (x):

First Result (y):

Second Result (z):

valueOf()

The valueOf() method returns the Primitive value of a String Object.

var x = "Hello World!";
var y = x.valueOf();

String (x):

Result (y):

| NOTICE |
The valueOf() method usually called automatically by Javascript behind the scenes, and not explicitly in code.

includes()

1)The includes() method determines Whether a string contains the character of a specified string.
2)This method returns true if the string contain the characters, false if not.
3)The includes() method case sensitive.
string.includes(searchValue , start);
4) start defines - At which position to start the search. default position is 0 .

var x = "Hello friends, welcome to sololearn.";
var y = x.includes("friends");
var z = x.includes("welcome" , 10);

String (x):

First result (y):

Second result (z):

localeCompare()

The localeCompare() method compares two string in the current locale.
The locale is based on the language settings of the browser.

var a = "Apple";
var b = "Bug";
var c = "Css";
var d = "Css";
var x = a.localeCompare(b);
var y = b.localeCompare(a);
var z = c.localeCompare(d);

Returns -1 if (a) is sorted before (b)
Returns 1 if (b) is sorted after (a)
Returns 0 if the two strings are equal

first Result (x):

Second Result (y):

Third Result (z):

startsWith()

1)The startsWith() method determines Whether a string Begins with the characters of a specified string.
2)This method returns true if the begin with the characters,and false if not.
3)The startsWith() method case sensitive.

var x =
"Hello friends, welcome to Sololearn";
var y = x.startsWith("welcome");
var z = x.startsWith("friends" , 6);

String (x):

First Result (y):

Second Result (z):

endsWith()

1)The endsWith() method determines Whether a string ends with the characters of a specified string.
2)This method return true if the string ends with the characters, and false if not.
3)The endsWith() method is case sensitive.
4)check if a string ends with "Hello",assuming the string is 5 characters long:

var x =
"Hello friends, welcome to Sololearn";
var y = x.endsWith("Sololearn");
var z = x.endsWith("Hello" , 5);

String (x):

First Result (y):

Second Result (z):

toLocaleLowerCase()

The localeLowerCase() method converts a string to Lowercase letters,according to the host's current locale.

var x = "WELCOME to SOLOLEARN";
var y = x.toLocaleLowerCase();

String (x):

Result (y):

toLocaleUpperCase()

The toLocaleUpperCase() method converts a string to UpperCase letters.according to the host's is current locale.

var x = "Welcome to Sololearn";
var y = x.toLocaleUpperCase();

String (x):

Result (y):

| NOTICE |
1)Generally, this method returns the same value as the toUpperCase() Method.
2)However, for some locales,where language conflict with the regular unicode
case mapping occurs(such as Turkish),the
retults may wary.
3)The locale is based on the language settings of the browser.

Array Methods

Coming Soon,. :-)

Other String Methods Resources

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Created By ☆Sampath👻

Javascript String Methods Full Tutorial