JavaScript JSON and Global Functions – Complete List with Examples

Global functions are available everywhere without a prefix. Several have stricter, clearer replacements on Number (Number.isNaN(), Number.parseInt()); prefer those in new code.

Name	Description	Since
`JSON.parse()`	Turn a JSON string into a JavaScript value. Throws SyntaxError on invalid JSON; an optional reviver transforms values.	ES5
`JSON.stringify()`	Convert a JavaScript value to a JSON string, optionally filtering keys and pretty-printing with indentation.	ES5
`parseInt()`	Parse an integer from the start of a string in a given base. Always pass the radix, e.g. parseInt("08", 10).	ES1
`parseFloat()`	Parse a decimal number from the start of a string, stopping at the first character that can't be part of it.	ES1
`isNaN()`	Return true if a value is NaN after converting it to a number, so isNaN("hello") is true. Prefer Number.isNaN().	ES1
`isFinite()`	Return true if a value is a finite number after converting it to a number. Prefer Number.isFinite() for strict checks.	ES1
`encodeURIComponent()`	Encode a string for use as one part of a URL (a query value or path segment), escaping &, =, ?, / and spaces.	ES3
`decodeURIComponent()`	Decode a URL component encoded by encodeURIComponent(), turning %20-style escapes back into characters.	ES3
`encodeURI()`	Encode a complete URL, leaving characters with special meaning in URLs (like :, /, ? and &) untouched.	ES3
`decodeURI()`	Decode a full URL encoded by encodeURI(), keeping escape sequences that represent reserved URL characters.	ES3
`structuredClone()`	Create a deep copy of a value, including nested objects, arrays, Dates, Maps and Sets. Functions can't be cloned.	HTML (2022)

Name

Description

Since

JSON.parse()

Turn a JSON string into a JavaScript value. Throws SyntaxError on invalid JSON; an optional reviver transforms values.

ES5

JSON.stringify()

Convert a JavaScript value to a JSON string, optionally filtering keys and pretty-printing with indentation.

ES5

parseInt()

Parse an integer from the start of a string in a given base. Always pass the radix, e.g. parseInt("08", 10).

ES1

parseFloat()

Parse a decimal number from the start of a string, stopping at the first character that can't be part of it.

ES1

isNaN()

Return true if a value is NaN after converting it to a number, so isNaN("hello") is true. Prefer Number.isNaN().

ES1

isFinite()

Return true if a value is a finite number after converting it to a number. Prefer Number.isFinite() for strict checks.

ES1

encodeURIComponent()

Encode a string for use as one part of a URL (a query value or path segment), escaping &, =, ?, / and spaces.

ES3

decodeURIComponent()

Decode a URL component encoded by encodeURIComponent(), turning %20-style escapes back into characters.

ES3

encodeURI()

Encode a complete URL, leaving characters with special meaning in URLs (like :, /, ? and &) untouched.

ES3

decodeURI()

Decode a full URL encoded by encodeURI(), keeping escape sequences that represent reserved URL characters.

ES3

structuredClone()

Create a deep copy of a value, including nested objects, arrays, Dates, Maps and Sets. Functions can't be cloned.

HTML (2022)