250 lines
8.4 KiB
Markdown
250 lines
8.4 KiB
Markdown
`jju` - a set of utilities to work with JSON / JSON5 documents
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[](https://www.npmjs.org/package/jju)
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[](https://travis-ci.org/rlidwka/jju)
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[](https://www.npmjs.org/package/jju)
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## Installation
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```
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yarn add jju
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```
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or
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```
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npm install jju
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```
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## Usage
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This module provides following functions:
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1. [jju.parse()](#jjuparse-function) parses json/json5 text and returns a javascript value it corresponds to
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2. [jju.stringify()](#jjustringify-function) converts javascript value to an appropriate json/json5 text
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3. [jju.tokenize()](#jjutokenize-function) parses json/json5 text and returns an array of tokens it consists of ([see demo](http://rlidwka.github.io/jju/tokenizer.html))
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4. [jju.analyze()](#jjuanalyze-function) parses json/json5 text and tries to guess indentation, quoting style, etc.
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5. [jju.update()](#jjuupdate-function) changes json/json5 text, preserving original formatting as much as possible ([see demo](http://rlidwka.github.io/jju/editor.html))
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All functions are able to work with a standard JSON documents. `jju.parse()` and `jju.stringify()` are better in some cases, but slower than native `JSON.parse()` and `JSON.stringify()` versions. Detailed description see below.
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### jju.parse() function
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```javascript
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/*
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* Main syntax:
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*
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* `text` - text to parse, type: String
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* `options` - parser options, type: Object
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*/
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jju.parse(text[, options])
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// compatibility syntax
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jju.parse(text[, reviver])
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```
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Options:
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- reserved\_keys - what to do with reserved keys (String, default="ignore")
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- "ignore" - ignore reserved keys
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- "throw" - throw SyntaxError in case of reserved keys
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- "replace" - replace reserved keys, this is the default JSON.parse behaviour, unsafe
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Reserved keys are keys that exist in an empty object (`hasOwnProperty`, `__proto__`, etc.).
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```javascript
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// 'ignore' will cause reserved keys to be ignored:
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parse('{hasOwnProperty: 1}', {reserved_keys: 'ignore'}) == {}
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parse('{hasOwnProperty: 1, x: 2}', {reserved_keys: 'ignore'}).hasOwnProperty('x') == true
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// 'throw' will cause SyntaxError in these cases:
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parse('{hasOwnProperty: 1}', {reserved_keys: 'throw'}) == SyntaxError
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// 'replace' will replace reserved keys with new ones:
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parse('{hasOwnProperty: 1}', {reserved_keys: 'replace'}) == {hasOwnProperty: 1}
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parse('{hasOwnProperty: 1, x: 2}', {reserved_keys: 'replace'}).hasOwnProperty('x') == TypeError
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```
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- null\_prototype - create object as Object.create(null) instead of '{}' (Boolean)
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if `reserved_keys != 'replace'`, default is **false**
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if `reserved_keys == 'replace'`, default is **true**
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It is usually unsafe and not recommended to change this option to false in the last case.
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- reviver - reviver function - Function
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This function should follow JSON specification
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- mode - operation mode, set it to 'json' if you want to throw on non-strict json files (String)
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### jju.stringify() function
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```javascript
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/*
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* Main syntax:
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*
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* `value` - value to serialize, type: *
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* `options` - serializer options, type: Object
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*/
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jju.stringify(value[, options])
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// compatibility syntax
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jju.stringify(value[, replacer [, indent])
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```
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Options:
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- ascii - output ascii only (Boolean, default=false)
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If this option is enabled, output will not have any characters except of 0x20-0x7f.
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- indent - indentation (String, Number or Boolean, default='\t')
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This option follows JSON specification.
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- quote - enquoting char (String, "'" or '"', default="'")
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- quote\_keys - whether keys quoting in objects is required or not (String, default=false)
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If you want `{"q": 1}` instead of `{q: 1}`, set it to true.
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- sort\_keys - sort all keys while stringifying (Boolean or Function, default=false)
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By default sort order will depend on implementation, with v8 it's insertion order. If set to `true`, all keys (but not arrays) will be sorted alphabetically. You can provide your own sorting function as well.
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- replacer - replacer function or array (Function or Array)
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This option follows JSON specification.
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- no\_trailing\_comma = don't output trailing comma (Boolean, default=false)
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If this option is set, arrays like this `[1,2,3,]` will never be generated. Otherwise they may be generated for pretty printing.
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- mode - operation mode, set it to 'json' if you want correct json in the output (String)
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Currently it's either 'json' or something else. If it is 'json', following options are implied:
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- options.quote = '"'
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- options.no\_trailing\_comma = true
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- options.quote\_keys = true
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- '\x' literals are not used
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### jju.tokenize() function
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```javascript
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/*
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* Main syntax:
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*
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* `text` - text to tokenize, type: String
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* `options` - parser options, type: Object
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*/
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jju.tokenize(text[, options])
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```
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Options are the same as for the `jju.parse` function.
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Return value is an array of tokens, where each token is an object:
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- raw (String) - raw text of this token, if you join all raw's, you will get the original document
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- type (String) - type of the token, can be `whitespace`, `comment`, `key`, `literal`, `separator` or `newline`
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- stack (Array) - path to the current token in the syntax tree
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- value - value of the token if token is a `key` or `literal`
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You can check tokenizer for yourself using [this demo](http://rlidwka.github.io/jju/tokenizer.html).
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### jju.analyze() function
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```javascript
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/*
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* Main syntax:
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*
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* `text` - text to analyze, type: String
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* `options` - parser options, type: Object
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*/
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jju.analyze(text[, options])
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```
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Options are the same as for the `jju.parse` function.
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Return value is an object defining a programming style in which the document was written.
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- indent (String) - preferred indentation
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- newline (String) - preferred newline
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- quote (String) - `"` or `'` depending on which quote is preferred
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- quote\_keys (Boolean) - `true` if unquoted keys were used at least once
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- has\_whitespace (Boolean) - `true` if input has a whitespace token
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- has\_comments (Boolean) - `true` if input has a comment token
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- has\_newlines (Boolean) - `true` if input has a newline token
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- has\_trailing\_comma (Boolean) - `true` if input has at least one trailing comma
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### jju.update() function
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```javascript
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/*
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* Main syntax:
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*
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* `text` - original text, type: String
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* `new_value` - new value you want to set
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* `options` - parser or stringifier options, type: Object
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*/
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jju.update(text, new_value[, options])
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```
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If you want to update a JSON document, here is the general approach:
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```javascript
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// here is your original JSON document:
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var input = '{"foo": "bar", "baz": 123}'
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// you need to parse it first:
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var json = jju.parse(input, {mode: 'json'})
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// json is { foo: 'bar', baz: 123 }
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// then you can change it as you like:
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json.foo = 'quux'
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json.hello = 'world'
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// then you run an update function to change the original json:
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var output = jju.update(input, json, {mode: 'json'})
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// output is '{"foo": "quux", "baz": 123, "hello": "world"}'
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```
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Look at [this demo](http://rlidwka.github.io/jju/editor.html) to test various types of json.
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## Advantages over existing JSON libraries
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In a few cases it makes sense to use this module instead of built-in JSON methods.
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Parser:
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- better error reporting with source code and line numbers
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In case of syntax error, JSON.parse does not return any good information to the user. This module does:
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```
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$ node -e 'require("jju").parse("[1,1,1,1,invalid]")'
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SyntaxError: Unexpected token 'i' at 0:9
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[1,1,1,1,invalid]
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^
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```
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This module is about 5 times slower, so if user experience matters to you more than performance, use this module. If you're working with a lot of machine-generated data, use JSON.parse instead.
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Stringifier:
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- util.inspect-like pretty printing
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This module behaves more smart when dealing with object and arrays, and does not always print newlines in them:
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```
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$ node -e 'console.log(require("./").stringify([[,,,],,,[,,,,]], {mode:"json"}))'
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[
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[null, null, null],
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null,
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null,
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[null, null, null, null]
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]
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```
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JSON.stringify will split this into 15 lines, and it's hard to read.
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Yet again, this feature comes with a performance hit, so if user experience matters to you more than performance, use this module. If your JSON will be consumed by machines, use JSON.stringify instead.
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As a rule of thumb, if you use "space" argument to indent your JSON, you'd better use this module instead.
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