Select 2 basic usage with Group, Search & Highlights

gistfile1.txt

Group, Simple Search, Highlight, Shorten Text with Tooltip
https://jsfiddle.net/gb7aju95/91/

Keyword Search, Highlight, 
https://jsfiddle.net/bzotcxrp/92/

Keyword Search, Highlight,
https://jsfiddle.net/bzotcxrp/200/

Complete String with Keyword Search and Highlight
http://jsfiddle.net/vzLmwrc7/62/

Example:

function customMatcher(params, data) {

    if ($.trim(params.term) === '') {
        return data;
    }

    if (typeof data.text === 'undefined') {
        return null;
    }
    
    if(params.term && params.term.length < 1){
        return data;
    }
    
    let terms = params.term.toUpperCase().split(' ');
    terms.unshift(params.term.toUpperCase().trim());

    let text = data.text.toUpperCase();
    
    terms = terms.filter(function(e) {
        let temp = String(e).trim();
        return (temp.length >= 1);
    });
    
    if(!terms.length){
        return data;
    }
    
    var filteredChildren = [];
    $.each(terms, function (id, term) {
        if (text.indexOf(term) >= 0 && term.length >= 1) {
            filteredChildren.push(data);
        }
    });

    if (filteredChildren.length) {
        var modifiedData = $.extend({}, data, true);
        modifiedData.data = filteredChildren;

        // You can return modified objects from here
        // This includes matching the `children` how you want in nested data sets
        return modifiedData;
    }

    // Return `null` if the term should not be displayed
    return null;
}
      
function highlightMatched(element, term, highlightRecursively = true) {
    var $result = $('<span></span>');
    
    if(term.length < 1){
        return $result.text(element.text);
    }
        
    let terms = term.toUpperCase().split(' ');
    terms.unshift(term.toUpperCase().trim());

    terms = terms.filter(function(e) {
        let temp = String(e).trim();
        return (temp.length >= 1);
    });
        
    if(!terms.length){
        return $result.text(element.text);
    }
    
    terms = [...new Set(terms)];
    
    removeHighlight(element.element);

    if(element.text.toUpperCase().indexOf(terms[0].toUpperCase()) >= 0){
        var regEx = new RegExp(terms[0], "ig");
        highlight(element.element, regEx, highlightRecursively);
    }else{
        $.each(terms, function (id, searchTerm) {
            let termMatch = element.text.toUpperCase().indexOf(searchTerm.toUpperCase());
                
            // If there is a match, execute ins
            if (termMatch >= 0) {
                var regEx = new RegExp(searchTerm, "ig");
                highlight(element.element, regEx, highlightRecursively);
            }
        });
    }
    
    return $result.html(element.element.innerHTML); 
}

function highlight(node, regex, highlightRecursively, isRecursiveCall = false) {
    var skip = 0;
    
    if (3 === node.nodeType) {
        var spannode, middleclone, middlebit = node.data.search(regex);
        
        if(0 <= middlebit && 0 < node.data.length) {
            middleclone = node.data.match(regex); 
            (spannode = document.createElement("span")).className = "highlight";
            (middlebit = node.splitText(middlebit)).splitText(middleclone[0].length);
            middleclone = middlebit.cloneNode(!0); 
            spannode.appendChild(middleclone); 
            middlebit.parentNode.replaceChild(spannode, middlebit);
            skip = 1;
        }
    } else if (1 === node.nodeType && node.childNodes && !/(script|style)/i.test(node.tagName) && ("highlight" !== node.className || "SPAN" !== node.tagName))
        for (var i = 0; i < node.childNodes.length; ++i){
            if(!highlightRecursively){
                if(!isRecursiveCall){
                    let temp = highlight(node.childNodes[i], regex, highlightRecursively, true);
                    if(temp == 1){
                        break;
                    }
                }
            }
            else{
                i += highlight(node.childNodes[i], regex, highlightRecursively);
            }
        } 
    
    return skip
}
         
function removeHighlight(element) {
    return $(element).find("span.highlight").each(function() {
        var parent = this.parentNode;
        parent.replaceChild(this.firstChild, this);
        parent.normalize();
    }).end()
}

function registerAutoFocusEvent(element){
    element.on('select2:open', () => {
        document.querySelector('.select2-search__field').focus();
    });
}

var query = {};

function mouldToSelect2(element, sort = false){
	element.select2({
		placeholder: "Your Placeholder",
		allowClear: true,
		width: '100%',
		dropdownAutoWidth: true,
		dropdownPosition: 'below',
		matcher: customMatcher,
		templateResult: function (item) {
			if (item.loading) {
				return item.text;
			}
			var term = query.term || '';
			
			totalOptions = element.find('option') ? element.find('option').length : 0;
			highlightRecursively = totalOptions > 2000 ? false : true;
			
			var $result = highlightMatched(item, term, highlightRecursively);
			return $result;
		},
		language: {
			searching: function (params) {
			// Intercept the query as it is happening
			query = params;
			// Change this to be appropriate for your application
			return 'Searching…';
			}
		},
        sorter: function(data) {
			if(sort){
				return data.sort(function(a, b) {
        			return a.text < b.text ? -1 : a.text > b.text ? 1 : 0;
    			});	
			}
    		return data;
		}
	}).on('select2:open', function(e){
		$('.select2-search__field').attr('placeholder', 'Search');
	});
}