How to use JSON.parse () in JavaScript
Editor to share with you how to use JSON.parse () in JavaScript. I hope you will get something after reading this article. Let's discuss it together.
JSON.parse () usage feature in JavaScript
When parsing JSON strings, you need to pay attention to some specifications of JSON format, otherwise it will be easy to report errors.
JSON data has strict rules on the type and format of values. The specific rules are as follows:
This method uses string type JSON formatted data.
This method also supports three types of values, namely, numeric, Boolean, and null, and converts them into corresponding literal values.
Other types are not supported.
JSON.parse ('China')
/ / 'China'
JSON.parse (null) / / null
JSON.parse (111.) / / 111
JSON.parse (0x12) / / 18
JSON.parse (true) / / true
JSON.parse ([])
/ / Uncaught SyntaxError: Unexpected end of JSON input
Strings must use double quotation marks, not single quotation marks.
JSON.parse ('"String"')
/ / 'String'
JSON.parse ('\ 'String\')
/ / Uncaught SyntaxError: Unexpected token'in JSON at position 0
Only decimal strings are supported, but numbers must be followed after the decimal point.
JSON.parse ('111') / / 111
JSON.parse ('0x12')
/ / Uncaught SyntaxError: Unexpected token x in JSON at position 1
JSON.parse ('111.232') / / 111.232
JSON.parse ('111.')
/ / Uncaught SyntaxError: Unexpected end of JSON input
Undefined, Symbol, and BigInt cannot be used, and numbers do not support NaN, Infinity, and-Infinity.
JSON.parse (undefined)
/ / Uncaught SyntaxError: Unexpected token u in JSON at position 0
JSON.parse (Symbol ())
/ / Uncaught TypeError: Cannot convert a Symbol value to a string
JSON.parse ('12n')
/ / Uncaught SyntaxError: Unexpected token n in JSON at position 2
Compound types can only be literals such as: [] and {}.
The object constructor cannot be used because it is treated as an execution statement and is not supported.
You cannot use Object and Array, nor can it be functions, RegExp objects, Date objects, Error objects, and so on.
JSON.parse ('[]')
/ / []
JSON.parse ('Object ()')
/ / Uncaught SyntaxError: Unexpected token O in JSON at position 0
The property name of an object must be in double quotation marks.
JSON.parse ('{"key": 1}')
/ / {key: 1}
JSON.parse ('{key: 1}')
/ / Uncaught SyntaxError: Unexpected token k in JSON at position 1
After the last member of an array or object, you cannot add a comma.
JSON.parse ('[1,2,3,4,]')
/ / VM2771:1 Uncaught SyntaxError: Unexpected token] in JSON at position 13
JSON.parse ('{"key": 1,}')
/ / VM2779:1 Uncaught SyntaxError: Unexpected token} in JSON at position 12
Support for unicode escape.
JSON.parse ('{"\ u0066": 333}')
/ / {f: 333}
Some control characters and escape characters are not supported, such as'\ n','\ t' and so on.
JSON.parse ('"\ n')
/ / Uncaught SyntaxError: Unexpected token
Other methods of parsing
There are other ways to convert a json string to a json object (js object value), but not safe code.
Const str ='{"name": "json", "age": 18}'
Const json = JSON.parse (str)
Const json = eval ("(" + str + ")")
Const json = (new Function ("return" + str))
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