string.md

title	section	prev	next
string	docs	label url Regular expressions /understanding-json-schema/reference/regular_expressions	label url Dialect and vocabulary declaration /understanding-json-schema/reference/schema

The string type is used for strings of text. It may contain Unicode characters.

[tabs-start "Language-specific info"]

[tab "Python"] In Python, "string" is analogous to the unicode type on Python

[tab "Ruby"] In Ruby, "string" is analogous to the String type.

[tab "Objective-C"] In Objective-C, "string" is analogous to the NSString type.

[tab "Swift"] In Swift, "string" is analogous to the String type.

[tabs-end]

// props { "isSchema": true }
{ "type": "string" }

// props { "indent": true, "valid": true }
"Déjà vu"

// props { "indent": true, "valid": true }
""

// props { "indent": true, "valid": true }
"42"

// props { "indent": true, "valid": false }
42

Length[#length]

The length of a string can be constrained using the minLength and maxLength keywords. For both keywords, the value must be a non-negative number.

// props { "isSchema": true }
{
  "type": "string",
  "minLength": 2,
  "maxLength": 3
}

// props { "indent": true, "valid": false }
"A"

// props { "indent": true, "valid": true }
"AB"

// props { "indent": true, "valid": true }
"ABC"

// props { "indent": true, "valid": false }
"ABCD"

Regular Expressions[#regexp]

The pattern keyword is used to restrict a string to a particular regular expression. The regular expression syntax is the one defined in JavaScript (ECMA 262 specifically) with Unicode support. See Regular Expressions for more information.

When defining the regular expressions, it's important to note that the string is considered valid if the expression matches anywhere within the string. For example, the regular expression "p" will match any string with a p in it, such as "apple" not just a string that is simply "p". Therefore, it is usually less confusing, as a matter of course, to surround the regular expression in ^...$, for example, "^p$", unless there is a good reason not to do so.

The following example matches a simple North American telephone number with an optional area code:

// props { "isSchema": true }
{
  "type": "string",
  "pattern": "^(\\([0-9]{3}\\))?[0-9]{3}-[0-9]{4}$"
}

// props { "indent": true, "valid": true }
"555-1212"

// props { "indent": true, "valid": true }
"(888)555-1212"

// props { "indent": true, "valid": false }
"(888)555-1212 ext. 532"

// props { "indent": true, "valid": false }
"(800)FLOWERS"