JavaScript String Search

String Search Methods

JavaScript String indexOf()

The indexOf() method returns the index (position) of the first occurrence of a string in a string, or it returns -1 if the string is not found:

Example

let text = "Please locate where 'locate' occurs!";

let index = text.indexOf("locate");

JavaScript String lastIndexOf()

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

Example

let text = "Please locate where 'locate' occurs!";

let index = text.lastIndexOf("locate");

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

Example

let text = "Please locate where 'locate' occurs!";

let index = text.lastIndexOf("John");

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

Example

let text = "Please locate where 'locate' occurs!";

let index = text.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 text = "Please locate where 'locate' occurs!";

text.lastIndexOf("locate", 15);

JavaScript String search()

The search() method searches a string for a string (or a regular expression) and returns the position of the match:

Examples

let text = "Please locate where 'locate' occurs!";

text.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 returns an array containing the results of matching a string against a string (or a regular expression).

Examples

let text = "The rain in SPAIN stays mainly in the plain";

text.match("ain");

JavaScript String matchAll()

The matchAll() method returns an iterator containing the results of matching a string against a string (or a regular expression).

Example

const iterator = text.matchAll("Cats");

If the parameter is a regular expression, the global flag (g) must be set, otherwise a TypeError is thrown.

Example

const iterator = text.matchAll(/Cats/g);

If you want to search case insensitive, the insensitive flag (i) must be set:

Example

const iterator = text.matchAll(/Cats/gi);

JavaScript String includes()

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

Otherwise it returns false.

Examples

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

text.includes("world");

JavaScript String startsWith()

The startsWith() method returns true if a string begins with a specified value.

Otherwise it returns false:

Examples

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

text.startsWith("Hello");

A start position for the search can be specified:

Example

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

text.startsWith("world", 5)

JavaScript String endsWith()

The endsWith() method returns true if a string ends with a specified value.

Otherwise it returns false:

Examples

let text = "John Doe";

text.endsWith("Doe");