JavaScript String Functions, Operators and Properties

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JavaScript String Functions, Operators and Properties

String used in examples below
`var str = "HTML tags start with “<” & end with “>”.";`

The results in the examples below are from actual working examples of JavaScript, resulting from running actual JavaScript code in your browser, rather than simply the expected results put in HTML code. For example, a locale-sensitive comparison as performed by localeCompare will be based on the locale in your browser.

String properties

	Result	String property		Use / Result
get only	Number	`string`.length		get length of String
get only	Number	Example:	`str.length`

String operators

Result	String operator		Use / Result
String	= `value`		String assignment operator (JavaScript equals)
String	Example:	`var newstr = "value"`	a String with a value of "value"
String	`string1` + `string2`		concatenate two Strings
String	Example:	`var newstr = "This is" + " a test.";`
String	+= `string2`		append a String to another String
String	Example:	`str += " Right on!";`

Static methods of String global object

Static Method			Use / Result
String	new String(`value`)		String constructor
	Examples:	`var newstr = new String("value")`	a String with a value of "value"
	Examples:	`var newstr = new String()`	an empty String
String	String(`object`)		cast `object` to String
String	Examples:	`String(obj)`
String	String.fromCharCode(`char1`[, ... `charN`])		create a String from character codes
	Examples:	`var newstr = String.fromCharCode(9733, 10003)`
	Examples:	`var newstr = String.fromCharCode(0x2605, 0x2713)`

String functions

Result	String function		Use / Result
String	`string`.charAt(`position`)		get character at position in string
String	Example:	`str.charAt(2)`
Number	`string`.charCodeAt(`position`)		get character code at position in string
Number	Example:	`str.charCodeAt(2)`
String	`string`.concat(`string1`[, ... `stringN`])		append one or more Strings
String	Example:	`str.concat(" ", "Right on!")`
Number	`string`.indexOf(`searchString`[, `position`])		find position of `searchString` within string; you can also search for a regular expression using String.search(/`regexp`/`flags`)
	Examples:	`str.indexOf("with")`
	Examples:	`str.indexOf("with", 16)`
Number	`string`.lastIndexOf(`searchString`[, `position`])		find last position of `searchString` within string
	Examples:	`str.lastindexOf("with")`
	Examples:	`str.lastindexOf("with", 31)`
Number	`string`.localeCompare(`string1`, `string2`)		locale-sensitive comparison of one string with another string Note that: comparison is dependent on the client system's locale, not the server-side system's locale, and although a case-sensitive comparision is used, which letter in the alphabet is considered a higher priority for determining order than its case - in English, for example, lower case comes before upper case, so the order of alphabetic characters is "a", "A", "b", "B", etc. (see examples below)
	Example:	`"A".localeCompare("a")`
		`"A".localeCompare("b")`
		`"a".localeCompare("B")`
Array	`string`.match(/`regexp`/[`flags`])		retrieve substrings of a String that match a given regular expression
Array	Example:	`str.match(/with/gi)`
String	`string`.replace(`searchString`, `replacement`) `string`.replace(/`regexp`/`flags`, `replacement`)		replace part of one string with another string
String	Example:	`str.replace("start", "begin")`
Number	`string`.search(/`regexp`/[`flags`])		get index of a substring that matches a regular expression; to match a string instead use String.indexOf(`substring`[, `position`])
Number	Example:	`str.search(/[^a-z\s]/i)`
String	`string`.slice(`start`, `end`)		get a substring of a string
String	Example:	`str.slice(16, 31)`
Array	`string`.split(`separator`[, `limit`]) `string`.split(/`regexp`/[, `limit`])		split String based on `separator`
	Examples:	`str.split(" ")[2] // third word`
		`str.split(/\s/)[3] // fourth word`
		`"first " + str.split(" ", 5).length + " of " + str.split(" ").length`
String	`string`.toLocaleLowerCase()		convert string to lower case based on client locale
String	Example:	`str.toLocaleLowerCase()`
String	`string`.toLocaleUpperCase()		convert string to upper case based on client locale
String	Example:	`str.toLocaleUpperCase()`
String	`string`.toLowerCase()		convert string to lower case
String	Example:	`str.toLowerCase()`
String	`string`.toString()		the String itself, same as String.valueOf()
String	Example:	`str.toString()`
String	`string`.toUpperCase()		convert string to upper case
String	Example:	`str.toUpperCase()`
String	`string`.trim()		remove leading and trailing spaces
String	Example:	`" TEST ".trim()`
String	`string`.valueOf()		the String itself, same as String.toString()
String	Example:	`str.valueOf()`

Global functions with String parameters

For the difference between encodeURI, encodeURIComponent and escape and information on the specific characters used for encoding, see JavaScript percent encoding functions.

Function / Operator			Use / Result
String	decodeURI(`encodedURI`)		decode an encoded URI
String	Examples:	`decodeURI("/The%20Firm/")`
String	decodeURIComponent(`encodedComponent`)		decode a query parameter or other encoded URI component
String	Examples:	`decodeURIComponent("decimal%E2%80%94To%E2%80%94%25") + "=" + decodeURIComponent("pct%20%3D%20dec%23%20*%20100")`
String	encodeURI(`unencodedURI`)		encode a URI
String	Examples:	`document.createElement("a").href = encodeURI("http://TVSeries.com/The Firm/");`
String	encodeURIComponent(`unencodedComponent`)		encode a query string parameter or other URI component
String	Examples:	`encodeURIComponent("decimal—To—%") + "=" + encodeURIComponent("pct = dec# * 100")`
String	escape(`string`)		deprecated escape all special characters in a string
String	Examples:	`escape("decimal—To—%") + "=" + escape("pct = dec# * 100")`
(any)	eval(`string1`[, ... `stringN`])		evaluate `string` as a JavaScript expression, returning the value of the last expression
(any)	Examples:	`eval(".67 * 100") + "%"`
Number	parseFloat(`string`)		convert String to a floating point Number
Number	Examples:	`var intval = parseFloat("123.45");`
Number	parseInt(`string`)		convert String to an integer Number
Number	Examples:	`var intval = parseInt("123");`

JSON functions

Result	JSON function		Result
Object	JSON.parse(`string`)		convert JSON string to JavaScript object
Object	Example:	`var obj = JSON.parse( '{"foo":"bar"}' )`
String	JSON.stringify(`object`)		convert JavaScript object to JSON string
String	Example:	`var newstr = JSON.stringify( { foo: "bar" } );`

Valid HTML 5