yoastseo-dep/src/languageProcessing/researches/metaDescriptionKeyword.js

Yoast clientside page analysis

import matchWords from "../helpers/match/matchTextWithArray";
import getSentences from "../helpers/sentence/getSentences";

/**
 * Replaces found keyword forms in the given description.
 *
 * @param {string}      description         The description to remove the matched keyword forms from.
 * @param {Object[]}    matchedKeywordForms The matched keyword forms to remove from the description.
 * @param {Number}      maxToRemove         The maximum amount of matches of each individual keyword to remove.
 *
 * @returns {string} The description with the keywords removed.
 */
const replaceFoundKeywordForms = function( description, matchedKeywordForms, maxToRemove ) {
	// Replace matches so we do not match them for synonyms.
	matchedKeywordForms.forEach( keywordForm =>
		keywordForm.matches.slice( 0, maxToRemove ).forEach(
			match => {
				description = description.replace( match, "" );
			}
		)
	);
	return description;
};

/**
 * Counts the number of full keyphrase matches in the given sentence. Takes synonyms into account.
 * A full keyphrase is when all keywords in the keyphrase match.
 *
 * @param {string}      sentence        The sentence that needs to be analyzed.
 * @param {Object}      topicForms      The keyphrase (and its optional synonyms') word forms.
 * @param {string}      locale          The current locale.
 * @param {function}    matchWordCustomHelper   The language-specific helper function to match word in text.
 *
 * @returns {Number} The number of matched keyphrases in the sentence.
 */
const matchPerSentence = function( sentence, topicForms, locale, matchWordCustomHelper ) {
	// Focus keyphrase matches.
	const matchesKeyphrase = topicForms.keyphraseForms.map( keywordForms => matchWords( sentence, keywordForms, locale, matchWordCustomHelper ) );
	// Count the number of matches that contain every word in the entire keyphrase.
	const fullKeyphraseMatches = Math.min( ...matchesKeyphrase.map( match => match.count ) );

	// Replace all full keyphrase matches so we do not match them for synonyms.
	sentence = replaceFoundKeywordForms( sentence, matchesKeyphrase, fullKeyphraseMatches );

	// Keyphrase synonyms matches.
	const fullSynonymsMatches = topicForms.synonymsForms.map(
		synonymForms => {
			// Synonym keyphrase matches.
			const matches = synonymForms.map( keywordForms => matchWords( sentence, keywordForms, locale, matchWordCustomHelper ) );
			// Count the number of matches that contain every word in the entire synonym keyphrase.
			const fullSynonymMatches = Math.min( ...matches.map( match => match.count ) );
			// Replace all full matches so we do not match them for other synonyms.
			sentence = replaceFoundKeywordForms( sentence, matchesKeyphrase, fullSynonymMatches );
			return fullSynonymMatches;
		}
	);

	return [ fullKeyphraseMatches, ...fullSynonymsMatches ].reduce( ( sum, count ) => sum + count, 0 );
};

/**
 * Counts the number of full keyphrase matches in the description.
 *
 * @param {Paper}       paper       The paper object containing the description.
 * @param {Researcher}  researcher  The researcher object to gather researchers from.
 *
 * @returns {Number} The number of keyphrase matches for the entire description.
 */
export default function( paper, researcher ) {
	const description = paper.getDescription();
	const locale = paper.getLocale();

	const topicForms = researcher.getResearch( "morphology" );
	const matchWordCustomHelper = researcher.getHelper( "matchWordCustomHelper" );
	const memoizedTokenizer = researcher.getHelper( "memoizedTokenizer" );

	const sentences = getSentences( description, memoizedTokenizer );

	const sentenceMatches = sentences.map(
		sentence => matchPerSentence( sentence, topicForms, locale, matchWordCustomHelper )
	);

	return sentenceMatches.reduce( ( sum, count ) => sum + count, 0 );
}