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eoghanmurrayeoghanmurray
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Add a slimDOM option to strip out unnecessary parts of the DOM (#36)
* Add a `slimDOM` option to strip out unnecessary parts of the DOM in terms of replay - <script> tags in the <head> take up unnecessary storage space and are often injected semi randomly to become a source of unnecessary variation between recordings of the same thing - comment tags can be stripped out without affecting display - future: this option could also turn on more aggressive stripping, e.g. elements that are hidden by CSS (assuming we can handle them becoming visible after mutation events) * Mark nodes ignored due to slimDOM option, so that they can also be ignored by the mutation observer in rrweb * Introducing the `ignored` attribute violates the `serializedNodeWithId` type * slimDOM: Strip out whitespace nodes from <head> element as they have no effect but take up space - these would otherwise have to be merged after <script> elements are removed; for statcounter usecase, removing <script> elements is no good if there is still a trace of their presence due to the white space (and hence a variant <head> node is still produced) - I explored a more radical stripping of all white space nodes, but there is a problem if parent node is <pre> or otherwise rendered with `white-space: pre` and similar. detecting applied styles with getComputedStyle would be very expensive (I haven't measured it though) * Export IGNORED_NODE as a constant instead of relying on the hard-to-grok `-2` * Remove <link rel=preload as=script> which are similarly as useless as <script> tags * Make slimDOM configurable with the expecations that `slimDOMOptions: true` will only enable non-destructive options (so not all options may be turned on) * Expand slimDOM to add options to remove more elements from the <head> that should not be necessary in the replayer context
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‎src/index.ts

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Original file line numberDiff line numberDiff line change
@@ -2,6 +2,7 @@ import snapshot, {
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serializeNodeWithId,
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transformAttribute,
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visitSnapshot,
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IGNORED_NODE,
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} from './snapshot';
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import rebuild, { buildNodeWithSN, addHoverClass } from './rebuild';
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export * from './types';
@@ -14,4 +15,5 @@ export {
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addHoverClass,
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transformAttribute,
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visitSnapshot,
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IGNORED_NODE,
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};

‎src/snapshot.ts

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@@ -6,11 +6,14 @@ import {
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INode,
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idNodeMap,
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MaskInputOptions,
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SlimDOMOptions,
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} from './types';
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let _id = 1;
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const tagNameRegex = RegExp('[^a-z1-6-_]');
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export const IGNORED_NODE = -2;
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function genId(): number {
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return _id++;
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}
@@ -323,6 +326,83 @@ function serializeNode(
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}
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}
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function lowerIfExists(maybeAttr : string | number | boolean) : string {
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if (maybeAttr === undefined) {
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return '';
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} else {
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return (maybeAttr as string).toLowerCase();
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}
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}
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function slimDOMExcluded(sn: serializedNode, slimDOMOptions: SlimDOMOptions): boolean {
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if (slimDOMOptions.comment && sn.type === NodeType.Comment) {
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// TODO: convert IE conditional comments to real nodes
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return true;
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} else if (sn.type === NodeType.Element) {
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if (slimDOMOptions.script &&
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(sn.tagName === 'script' ||
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(sn.tagName === 'link' && sn.attributes.rel === 'preload' && sn.attributes['as'] === 'script')
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)) {
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return true;
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} else if (slimDOMOptions.headFavicon && (
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(sn.tagName === 'link' && sn.attributes.rel === 'shortcut icon')
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|| (sn.tagName === 'meta' && (
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lowerIfExists(sn.attributes['name']).match(/^msapplication-tile(image|color)$/)
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|| lowerIfExists(sn.attributes['name']) === 'application-name'
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|| lowerIfExists(sn.attributes['rel']) === 'icon'
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|| lowerIfExists(sn.attributes['rel']) === 'apple-touch-icon'
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|| lowerIfExists(sn.attributes['rel']) === 'shortcut icon'
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)))) {
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return true;
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} else if (sn.tagName === 'meta') {
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if (slimDOMOptions.headMetaDescKeywords && (
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lowerIfExists(sn.attributes['name']).match(/^description|keywords$/)
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)) {
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return true;
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} else if (slimDOMOptions.headMetaSocial && (
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lowerIfExists(sn.attributes['property']).match(/^(og|twitter|fb):/) // og = opengraph (facebook)
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|| lowerIfExists(sn.attributes['name']).match(/^(og|twitter):/)
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|| lowerIfExists(sn.attributes['name']) === 'pinterest'
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)) {
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return true;
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} else if (slimDOMOptions.headMetaRobots && (
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lowerIfExists(sn.attributes['name']) === 'robots'
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|| lowerIfExists(sn.attributes['name']) === 'googlebot'
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|| lowerIfExists(sn.attributes['name']) === 'bingbot'
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)) {
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return true;
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} else if (slimDOMOptions.headMetaHttpEquiv && (
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sn.attributes['http-equiv'] !== undefined
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)) {
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// e.g. X-UA-Compatible, Content-Type, Content-Language,
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// cache-control, X-Translated-By
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return true;
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} else if (slimDOMOptions.headMetaAuthorship && (
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lowerIfExists(sn.attributes['name']) === 'author'
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|| lowerIfExists(sn.attributes['name']) === 'generator'
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|| lowerIfExists(sn.attributes['name']) === 'framework'
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|| lowerIfExists(sn.attributes['name']) === 'publisher'
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|| lowerIfExists(sn.attributes['name']) === 'progid'
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|| lowerIfExists(sn.attributes['property']).match(/^article:/)
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|| lowerIfExists(sn.attributes['property']).match(/^product:/)
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)) {
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return true;
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} else if (slimDOMOptions.headMetaVerification && (
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lowerIfExists(sn.attributes['name']) === 'google-site-verification'
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|| lowerIfExists(sn.attributes['name']) === 'yandex-verification'
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|| lowerIfExists(sn.attributes['name']) === 'csrf-token'
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|| lowerIfExists(sn.attributes['name']) === 'p:domain_verify'
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|| lowerIfExists(sn.attributes['name']) === 'verify-v1'
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|| lowerIfExists(sn.attributes['name']) === 'verification'
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|| lowerIfExists(sn.attributes['name']) === 'shopify-checkout-api-token'
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)) {
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return true;
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}
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}
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}
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return false;
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}
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export function serializeNodeWithId(
327407
n: Node | INode,
328408
doc: Document,
@@ -331,7 +411,9 @@ export function serializeNodeWithId(
331411
skipChild = false,
332412
inlineStylesheet = true,
333413
maskInputOptions?: MaskInputOptions,
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slimDOMOptions: SlimDOMOptions = {},
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recordCanvas?: boolean,
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preserveWhiteSpace = true,
335417
): serializedNodeWithId | null {
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const _serializedNode = serializeNode(
337419
n,
@@ -346,15 +428,26 @@ export function serializeNodeWithId(
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console.warn(n, 'not serialized');
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return null;
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}
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let id;
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// Try to reuse the previous id
351434
if ('__sn' in n) {
352435
id = n.__sn.id;
436+
} else if (slimDOMExcluded(_serializedNode, slimDOMOptions) ||
437+
(!preserveWhiteSpace &&
438+
_serializedNode.type === NodeType.Text &&
439+
!_serializedNode.isStyle &&
440+
!_serializedNode.textContent.replace(/^\s+|\s+$/gm,'').length
441+
)) {
442+
id = IGNORED_NODE;
353443
} else {
354444
id = genId();
355445
}
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const serializedNode = Object.assign(_serializedNode, { id });
357447
(n as INode).__sn = serializedNode;
448+
if (id === IGNORED_NODE) {
449+
return null; // slimDOM
450+
}
358451
map[id] = n as INode;
359452
let recordChild = !skipChild;
360453
if (serializedNode.type === NodeType.Element) {
@@ -367,6 +460,14 @@ export function serializeNodeWithId(
367460
serializedNode.type === NodeType.Element) &&
368461
recordChild
369462
) {
463+
if (
464+
(slimDOMOptions.headWhitespace &&
465+
_serializedNode.type === NodeType.Element &&
466+
_serializedNode.tagName == 'head')
467+
// would impede performance: || getComputedStyle(n)['white-space'] === 'normal'
468+
) {
469+
preserveWhiteSpace = false;
470+
}
370471
for (const childN of Array.from(n.childNodes)) {
371472
const serializedChildNode = serializeNodeWithId(
372473
childN,
@@ -376,7 +477,9 @@ export function serializeNodeWithId(
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skipChild,
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inlineStylesheet,
378479
maskInputOptions,
480+
slimDOMOptions,
379481
recordCanvas,
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preserveWhiteSpace,
380483
);
381484
if (serializedChildNode) {
382485
serializedNode.childNodes.push(serializedChildNode);
@@ -391,6 +494,7 @@ function snapshot(
391494
blockClass: string | RegExp = 'rr-block',
392495
inlineStylesheet = true,
393496
maskAllInputsOrOptions: boolean | MaskInputOptions,
497+
slimDOMSensibleOrOptions: boolean | SlimDOMOptions,
394498
recordCanvas?: boolean,
395499
): [serializedNodeWithId | null, idNodeMap] {
396500
const idNodeMap: idNodeMap = {};
@@ -416,6 +520,25 @@ function snapshot(
416520
: maskAllInputsOrOptions === false
417521
? {}
418522
: maskAllInputsOrOptions;
523+
const slimDOMOptions: SlimDOMOptions =
524+
(slimDOMSensibleOrOptions === true ||
525+
slimDOMSensibleOrOptions === 'all')
526+
// if true: set of sensible options that should not throw away any information
527+
? {
528+
script: true,
529+
comment: true,
530+
headFavicon: true,
531+
headWhitespace: true,
532+
headMetaDescKeywords: slimDOMSensibleOrOptions === 'all', // destructive
533+
headMetaSocial: true,
534+
headMetaRobots: true,
535+
headMetaHttpEquiv: true,
536+
headMetaAuthorship: true,
537+
headMetaVerification: true,
538+
}
539+
: slimDOMSensibleOrOptions === false
540+
? {}
541+
: slimDOMSensibleOrOptions;
419542
return [
420543
serializeNodeWithId(
421544
n,
@@ -425,6 +548,7 @@ function snapshot(
425548
false,
426549
inlineStylesheet,
427550
maskInputOptions,
551+
slimDOMOptions,
428552
recordCanvas,
429553
),
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idNodeMap,

‎src/types.ts

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Original file line numberDiff line numberDiff line change
@@ -87,3 +87,16 @@ export type MaskInputOptions = Partial<{
8787
textarea: boolean;
8888
select: boolean;
8989
}>;
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91+
export type SlimDOMOptions = Partial<{
92+
script: boolean;
93+
comment: boolean;
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headFavicon: boolean;
95+
headWhitespace: boolean;
96+
headMetaDescKeywords: boolean;
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headMetaSocial: boolean;
98+
headMetaRobots: boolean;
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headMetaHttpEquiv: boolean;
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headMetaAuthorship: boolean;
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headMetaVerification: boolean;
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}>;

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