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Extracts all JSON objects from an arbitrary text document.
The primary use-case is extracting structured data from non-structured documents, e.g. when scraping websites, it is common that HTML embeds JSON or JSON-like data structures.
<script>
$(document).on('BookingApp:SeatingPlan:Ready', () => {
$(document).trigger('BookingApp:StartSeatingPlanOnly', {
"sessionId": "438a8373-5fab-4d36-ac92-053ae2d04e9c"
});
});
</script>
The way that the crack-json
is intended to be used is that the scraper must narrow down the document to the HTML containing the subject JSON data and then crack-json
is used to extract all JSON-like objects. If in the above example we are interested in extracting the sessionId
, then it would be sufficient to get innerHTML
of the script
tag, use crack-json
to extract all JSON-like objects, and search for the matching object, e.g.
const session = extractJson(document.querySelector('script').innerHTML)
.find((maybeTargetSubject) => {
return maybeTargetSubject.sessionId;
});
session;
// {
// "sessionId": "438a8373-5fab-4d36-ac92-053ae2d04e9c"
// }
crack-json
iterates through the input text by searching for characters that indicate the start of a JSON object, array or text entity, and attempts to match the closing character and parse the resulting string. crack-json
iterates through document this way until it finds all text entities that can be parsed as JSON.
crack-json
extracts a single function: extractJson
.
import {
extractJson
} from 'crack-json';
extractJson
API/**
* @property filter Used to filter out strings before attempting to decode them.
* @property parser A parser used to extract JSON from the suspected strings. Default: `JSON.parse`.
*/
type ExtractJsonConfigurationType = {|
+filter?: (input: string) => boolean,
+parser?: (input: string) => any,
|};
type ExtractJsonType = (subject: string, configuration?: ExtractJsonConfigurationType) => any;
extractJson: ExtractJsonType;
import {
extractJson
} from 'crack-json';
const payload = `
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus ultricies laoreet malesuada. In feugiat augue non tristique pharetra. Duis nisl odio, vulputate maximus suscipit sit amet, ultrices vel lacus.
{"foo": "bar"}
Suspendisse volutpat risus id nibh lacinia, in placerat urna luctus. Phasellus condimentum nec ipsum ut tincidunt. Nullam aliquam euismod ante, vitae accumsan leo egestas a. Aliquam sed lacus nisl. Pellentesque nec hendrerit sem.
[{"baz": "qux"}]
Phasellus iaculis dui nec purus imperdiet placerat non sit amet odio. Donec pretium, arcu ac suscipit imperdiet, tellus orci convallis leo, non laoreet tortor lectus at dolor. Aenean tellus diam, imperdiet nec eleifend at, fermentum sit amet tellus. Vestibulum id purus ac mauris eleifend iaculis.
"quux"
Vestibulum sit amet quam tellus. Nulla facilisi.
`;
console.log(extractJson(payload));
Output:
[
{
foo: 'bar'
},
[
{
baz: 'qux'
}
],
'quux'
]
You can use filter
to exclude strings before they are parsed using an arbitrary condition. This will improve performance and reduce output only to the desirable objects, e.g.
import {
extractJson
} from 'crack-json';
const payload = `
<script>
const foo = {
cinemaId: '1',
};
const bar = {
venueId: '1',
};
const baz = {
userId: '1',
};
</script>
`;
console.log(extractJson(payload, {
filter: (input) => {
return input.includes('userId')
},
}));
Output:
[
{
userId: '1',
},
]
FAQs
Extracts all JSON objects from an arbitrary text document.
We found that crack-json demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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