Extracts keywords and quoted phrases from a Solr query string, ignoring field phrases, ranges and query syntax characters. Surrounds terms found with a <b> tag. Native javascript, no dependencies.

andi.highlight.js

andi.highlightTerms = [];

andi.highlight = function (el, terms) {
  if (terms === null || terms.length === 0) return;
  var term = terms.join('|');
  var regex = new RegExp('\\b('+term+')\\b', 'gi');
  if (el.innerHTML.match(regex) !== null) {
    el.innerHTML = el.innerHTML.replace(regex, '<b>$1</b>');
    el.classList === true ? el.classList.add('highlighted') : el.className += ' ' + 'highlighted';
  }
}

andi.highlightAll = function (selector, terms) {
  var els = document.querySelectorAll(selector);
  // note: els is a NodeList, not an array
  Array.prototype.forEach.call(els, function (el) {
    andi.highlight(el, terms);
  })
};

andi.parseHighlightTerms = function (solrquery) {
  // reject patterns
  var s = solrquery
    .replace(/[\w-]+:\((?=[^\)]*\))+[^\)]+\)+/g, '') // field:(value)
    .replace(/[\w-]+:\[(?=[^\]]*\])+[^\]]+\]+/g, '') // field:[value]
    .replace(/[\w-]+:\u0022(?=[^\u0022]+\u0022)+[^\u0022]+\u0022+/g, '') // field:"value"
    .replace(/[\w-]+:[^\s]*/g, '') // field:value
    .replace(/\[(?=[^\]]*\])+[^\]]+\]+/g, '') // [value TO value]
    .replace(/(^|\s)-\w+\b/g, '') // -value
    .replace(/NOT\s\w+\b/g, '') // NOT value
    .replace(/(AND|OR|NOT)/g, ''); // AND OR NOT
  // split string on whitespace and respect double quoted phrases
  var rawTerms = s.match(/(\u0022[^\u0022]*\u0022)|([^\u0022\s]+(\s|$))/g);
  var terms = [];
  rawTerms.forEach(function (rawTerm) {
    // trim whitespace, quotes, apostrophes and query syntax special chars
    var term = rawTerm
      .replace(/^[\s\u0022\u0027+-][\s\u0022\u0027+-]*/, '')
      .replace(/[\s*~\u0022\u0027][\s*~\u0022\u0027]*$/, '')
      .replace(/(\^|~)\d+$/, ''); // value^5, value~5
    if (term !== '') {
      terms.push(term);
    }
  });
  return terms;
};

$(document).ready(function () {
  // todo: should probably get query terms from some dedicated source instead of the q input.
  andi.highlightTerms = andi.parseHighlightTerms(document.getElementById('q').getAttribute('value'));
  if (andi.highlightTerms.length > 0) {
    andi.highlightAll('.and-citation-brief dd', andi.highlightTerms);
  }
})