A simple full-text-search algorithm

full-text-search-algorithm.js

// Draft 2
ngm.service('searchArray', function(){
  let THRESHHOLD = 0;
  let FULL_EXACTMATCH_MODIFIER  = 1.0;
  let FULL_STARTSWITH_MODIFIER  = 0.9;
  let FULL_CONTAINS_MODIFIER    = 0.3;
  let FULL_PARTIAL_MODIFIER     = 0.3;
  let PRECISION = 2;
  let re = /[\s\b]+/g;
  let search = (term, arr, key) => {
    let items = [];
    if(!term) items = arr.map((item)=>{
      delete item.$rel;
      return item;
    });
    else{
      let lowerTerm = term.toLowerCase();
      let terms = lowerTerm.split(re).filter(Boolean);
      arr.forEach((value)=>{
        let lowerValue = value[key].toLowerCase();
        let tokens = lowerValue.toLowerCase().split(re).filter(Boolean);
        let exactMatchScore   = FULL_EXACTMATCH_MODIFIER * (lowerValue === lowerTerm ? 1 : 0);
        let startsWithScore   = FULL_STARTSWITH_MODIFIER * (lowerValue !== lowerTerm && lowerValue.startsWith(lowerTerm) ? 1 : 0) * (lowerTerm.length / lowerValue.length);
        let containsScore     = FULL_CONTAINS_MODIFIER * (lowerTerm.length / lowerValue.length) * (lowerValue.indexOf(lowerTerm) > 0 ? 1 : 0);
        let partialMatchScore = FULL_PARTIAL_MODIFIER * terms.map((term, i)=>{
          let exactMatchCount = tokens.filter(token => term === token).length ? 1 : 0;
          let tokenStartsWithLength = tokens.reduce((acc, token)=>{
            if(!token.startsWith(term)) return acc;
            return Math.max(token.length, acc);
          }, 0);
          let startsWithCount = tokenStartsWithLength ? (term.length / tokenStartsWithLength) : 0;
          let tokenContainsLength = tokens.reduce((acc, token)=>{
            if(token.indexOf(term) < 1) return acc;
            return Math.max(token.length, acc);
          }, 0);
          let containsCount = tokenContainsLength ? (term.length / tokenContainsLength) : 0;
          return Math.max(exactMatchCount, startsWithCount, containsCount);
        }).reduce((x, y) => x + y) / (tokens.length + terms.length);
        value.$rel = {
          exactMatchScore,
          startsWithScore,
          containsScore,
          partialMatchScore,
          toString(){
            return `r${this.valueOf().toFixed(PRECISION)} - e${this.exactMatchScore.toFixed(PRECISION)} - s${this.startsWithScore.toFixed(PRECISION)} - c${this.containsScore.toFixed(PRECISION)} - p${this.partialMatchScore.toFixed(PRECISION)}`;
          },
          valueOf(){
            return Math.max(
              this.exactMatchScore,
              this.startsWithScore,
              ((this.containsScore + this.partialMatchScore) / 2)
            );
          }
        };
        if(value.$rel > THRESHHOLD) items.push(value);
      });
    }
    return items.sort((a, b)=>{
      if(a.$rel > b.$rel) return -1;
      if(a.$rel < b.$rel) return 1;
      if(a[key] < b[key]) return -1;
      if(a[key] > b[key]) return 1;
      return 0;
    });
  }
  return search;
});











// Draft 1
ngm.service('searchArray', function(){
  let re = /[\s\b]+/g;
  let threshhold = 0;
  let search = (term, arr, key) => {
    if(!term) return arr;
    let items = [];
    let lowerTerm = term.toLowerCase();
    let terms = lowerTerm.split(re).filter(Boolean);
    arr.forEach((value)=>{
      let lowerValue = value[key].toLowerCase();
      let tokens = lowerValue.toLowerCase().split(re).filter(Boolean);
      let partialMatchScore = tokens.map((token, i)=>{
        let exactMatchCount = 1.0 * (terms.filter(y => token === y).length / tokens.length);
        let startsWithCount = 0.5 * (terms.filter(y => token.startsWith(y)).length / tokens.length);
        let containsCount   = 0.1 * (terms.filter(y => token.indexOf(y) > 0 && y.length > 1).length / tokens.length);
        return (exactMatchCount + startsWithCount + containsCount) * ( 1 + (1/(i + 100)) );
      }).reduce((x, y) => x + y);
      let exactMatchScore = 1.0 * (lowerValue === lowerTerm ? 1 : 0);
      let startsWithScore = 0.1 * (lowerValue.startsWith(lowerTerm) ? 1 : 0);
      let rel = ((partialMatchScore + startsWithScore + exactMatchScore) / 2.6).toFixed(5);
      if(rel > threshhold) items.push({ rel, value, scores: {
        partialMatchScore,
        startsWithScore,
        exactMatchScore
      } });
    });
    return items.sort((a, b)=>{
      if(a.rel > b.rel) return -1;
      if(a.rel < b.rel) return 1;
      return 0;
    }).map(x => x.value);
  }
  return search;
});