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import { isPOJO } from '@amp/web-apps-utils';
// NOTE: be careful with imports here. This file is imported by browser code,
// so we expect tree shaking to only keep these functions.
const SERVER_DATA_ID = 'serialized-server-data';
// Take care with < (which has special meaning inside script tags)
// See: https://github.com/sveltejs/kit/blob/ff9a27b4/packages/kit/src/runtime/server/page/serialize_data.js#L4-L28
const replacements = {
'<': '\\u003C',
'\u2028': '\\u2028',
'\u2029': '\\u2029',
};
const pattern = new RegExp(`[${Object.keys(replacements).join('')}]`, 'g');
/**
* Serializes a POJO into a HTML <script> tag that can be read clientside by
* `deserializeServerData`.
*
* Use this to share data between serverside and clientside. Include the
* returned HTML in the response to a client to allow it to read this data.
*
* @param data data to serialize
* @returns serialized data (or empty string if serialization fails)
*/
export function serializeServerData(data: object): string {
try {
const sanitizedData = JSON.stringify(data).replace(
pattern,
(match) => replacements[match as keyof typeof replacements],
);
return `<script type="application/json" id="${SERVER_DATA_ID}">${sanitizedData}</script>`;
} catch (e) {
// Don't let recursive data (or other non-serializable things) throw.
// We'd rather just let the serialize no-op to avoid breaking consumers.
return '';
}
}
/**
* Deserializes data serialized on the server by `serializeServerData`.
*
* @returns deserialized data (or undefined if it doesn't exist/errors)
*/
export function deserializeServerData(): ReturnType<JSON['parse']> | undefined {
const script = document.getElementById(SERVER_DATA_ID);
if (!script) {
return;
}
script.parentNode?.removeChild(script);
try {
return JSON.parse(script.textContent || '');
} catch (e) {
// If the content is malformed, we want to avoid throwing. This
// situation should be impossible since we control the serialization
// above.
return;
}
}
/**
* JSON stringify a POJO value in a stable manner. Specifically, this means that
* objects which are structurally equal serialize to the same string.
*
* This is useful when comparing objects serialized by a server against objects
* build in browser. With plain JSON.stringify(), property order matters and is
* not guaranteed to be the same. In other words these two objects would
* JSON.stringify() differently:
*
* { a: 1, b: 2 }
* { b: 2, a: 1 }
*
* But these are structurally equal--they have the same keys and values.
*
* The expected use case for this function is generating keys for a Map for
* objects from a server that will be compared against objects from the browser.
* This function should be used on objects returned from `deserializeServerData`
* before they are used in such contexts.
*
* See: https://stackoverflow.com/a/43049877
*/
export function stableStringify(data: unknown): string {
if (Array.isArray(data)) {
const items = data.map(stableStringify).join(',');
return `[${items}]`;
}
// Sort object keys before serializing
if (isPOJO(data)) {
const keys = [...Object.keys(data)];
keys.sort();
const properties = keys
// undefined values should not get included in stringification
.filter((key) => typeof data[key] !== 'undefined')
.map(
(key) => `${JSON.stringify(key)}:${stableStringify(data[key])}`,
)
.join(',');
return `{${properties}}`;
}
return JSON.stringify(data);
}
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