JavaScript String Search

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JavaScript String Search


String Search Methods

String indexOf()
String lastIndexOf()
String search()
String match()
String matchAll()
String includes()
String startsWith()
String endsWith()


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

Example

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

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

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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");

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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);

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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);

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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");

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

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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
Perform a search for "ain":

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

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Perform a search for "ain":

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

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Perform a global search for "ain":

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

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Perform a global, case-insensitive search for "ain":

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

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Note
If a regular expression does not include the g modifier (global search),
match() will return only the first match in the string.
Read more about regular expressions in the chapter JS RegExp.



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");

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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);

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

Example

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

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Notes
matchAll() is an ES2020 feature.
matchAll() does not work in Internet Explorer.


JavaScript String includes()
The includes() method returns true if a string contains a specified value.
Otherwise it returns false.

Examples
Check if a string includes "world":

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

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Check if a string includes "world". Start at position 12:

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

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Notes
includes() is case sensitive.
includes() is an ES6 feature.
includes() is not supported in Internet Explorer.


JavaScript String startsWith()
The startsWith() method returns true
if a string begins with a specified value.
Otherwise it returns false:

Examples
Returns true:

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

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Returns false:

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

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A start position for the search can be specified:

Returns false:

let text = "Hello world, welcome to the universe.";
text.startsWith("world", 5)

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Returns true:

let text = "Hello world, welcome to the universe.";
text.startsWith("world", 6)

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Notes
startsWith() is case sensitive.
startsWith() is an ES6 feature.
startsWith() is not supported in Internet Explorer.


JavaScript String endsWith()
The endsWith() method returns true
if a string ends with a specified value.
Otherwise it returns false:

Examples
Check if a string ends with "Doe":

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

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

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

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Notes
endsWith() is case sensitive.
endsWith() is an ES6 feature.
endsWith() is not supported in Internet Explorer.



Complete String Reference
For a complete String reference, go to our:
Complete JavaScript String Reference.
The reference contains descriptions and examples of all string properties and methods.












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Reference: https://www.w3schools.com/js/js_string_search.asp