© 2023 AposTube

Learn JS #13

June 14 • 3:31 pm

Tags:

JavaScript String Search

JavaScript Search Methods

  • String indexOf()
  • String lastIndexOf()
  • String startsWith()
  • String endsWith()

JavaScript String indexOf()

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

Example

let str = "Please locate where 'locate' occurs!";
str.indexOf("locate");

Note:

  • JavaScript counts positions from zero.
  • 0 is the first position in a string, 1 is the second, 2 is the third, …

JavaScript String lastIndexOf()

The lastIndexOf() method returns the index of the last occurrence of a specified text in a string:

Example

let str = "Please locate where 'locate' occurs!";
str.lastIndexOf("locate");

Both indexOf(), and lastIndexOf() return -1 if the text is not found:

Example

let str = "Please locate where 'locate' occurs!";
str.lastIndexOf("John");

Both methods accept a second parameter as the starting position for the search:

Example

let str = "Please locate where 'locate' occurs!";
str.indexOf("locate", 15);

The lastIndexOf() methods searches backwards (from the end to the beginning), meaning: if the second parameter is 15, the search starts at position 15, and searches to the beginning of the string.

Example

let str = "Please locate where 'locate' occurs!";
str.lastIndexOf("locate", 15);

JavaScript String search()

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

Example

let str = "Please locate where 'locate' occurs!";
str.search("locate");

Did You Notice?

The two methods, indexOf() and search(), are equal?

They accept the same arguments (parameters), and return the same value?

The two methods are NOT equal. These are the differences:

  • The search() method cannot take a second start position argument.
  • The indexOf() method cannot take powerful search values (regular expressions).

You will learn more about regular expressions in a later chapter.

JavaScript String match()

The match() method searches a string for a match against a regular expression, and returns the matches, as an Array object.

Example 1

Search a string for “ain”:

let text = "The rain in SPAIN stays mainly in the plain";
text.match(/ain/g);

Example 2

Perform a global, case-insensitive search for “ain”:

let text = "The rain in SPAIN stays mainly in the plain";
text.match(/ain/gi);

JavaScript String includes()

The includes() method returns true if a string contains a specified value.

Example

let text = "Hello world, welcome to the universe.";
text.includes("world");

Syntax

string.includes(searchvalue, start)
searchvalue Required. The string to search for
start Optional. Default 0. Position to start the search
Returns: Returns true if the string contains the value, otherwise false
JS Version: ES6 (2015)

Check if a string includes “world”, starting the search at position 12:

let text = "Hello world, welcome to the universe.";
text.includes("world", 12);

JavaScript String startsWith()

The startsWith() method returns true if a string begins with a specified value, otherwise false:

Example

let text = "Hello world, welcome to the universe.";

text.startsWith("Hello");

Syntax

string.startsWith(searchvalue, start)

Parameter Values

Parameter Description
searchvalue Required. The value to search for.
start Optional. Default 0. The position to start the search.

Examples

let text = "Hello world, welcome to the universe.";

text.startsWith("world")    // Returns false

let text = "Hello world, welcome to the universe.";

text.startsWith("world", 5)    // Returns false

let text = "Hello world, welcome to the universe.";

text.startsWith("world", 6)    // Returns true

Note: The startsWith() method is case sensitive.

JavaScript String endsWith()

The endsWith() method returns true if a string ends with a specified value, otherwise false:

Example

Check if a string ends with “Doe”:

let text = "John Doe";
text.endsWith("Doe");

Syntax

string.endsWith(searchvalue, length)

Parameter Values

Parameter Description
searchvalue Required. The value to search for.
length Optional. The length to search.

Check if the 11 first characters of a string ends with “world”:

let text = "Hello world, welcome to the universe.";
text.endsWith("world", 11);

Note: The endsWith() method is case sensitive.

Apostube

See author's posts

Categories

Prev
Next

193 Responses

  99. Everything what you want to know about pills. safe and effective drugs are available.
    lisinopril 10
    Cautions. Prescription Drug Information, Interactions & Side.

    Reply

  104. Comprehensive side effect and adverse reaction information. drug information and news for professionals and consumers. avodart pills
    Drug information. Long-Term Effects.

    Reply

  111. earch our drug database. Cautions.
    https://finasteridest.com/ where to get generic propecia without rx
    Prescription Drug Information, Interactions & Side. Some are medicines that help people when doctors prescribe.

    Reply

  116. Prescription Drug Information, Interactions & Side. Get information now.
    clomid for sale
    drug information and news for professionals and consumers. Definitive journal of drugs and therapeutics.

    Reply

Leave a Reply

Your email address will not be published. Required fields are marked *

© 2023 AposTube. Built with ❤️ using WordPress and Ketos Theme.