Skip to content

isJSON

Import from @varavel/vdl-plugin-sdk/utils/predicates.

function isJSON(value): value is string;

Checks if a given value is a valid JSON string.

A valid JSON string is one that can be successfully parsed using JSON.parse(). According to JSON specifications, valid JSON can represent: - Objects (with string keys and valid JSON values) - Arrays (containing valid JSON values) - Strings - Numbers - Booleans - null

String values like "null", "true", "false", and numeric strings (e.g., "42") are considered valid JSON and will return true.

This function serves as a type guard in TypeScript, narrowing the type of the argument to string.

Parameters

Parameter Type Description
value unknown The value to check.

Returns

value is string

Returns true if value is a valid JSON string, else false.

Example

isJSON('{"name":"John","age":30}'); // true
isJSON('[1,2,3]'); // true
isJSON('true'); // true
isJSON('invalid json'); // false
isJSON({ name: 'John' }); // false (not a string)
isJSON(null); // false (not a string)