Highlight the search text - angular 2

user_8089526 0
Viewed 50741

A messenger displays the search results based on the input given by the user. Need to highlight the word that is been searched, while displaying the result. These are the html and component that is been used.

Component.html

 <div *ngFor = "let result of resultArray">
<div>Id : result.id </div>
<div>Summary : result.summary </div>
<div> Link : result.link </div>
</div>

Component.ts

resultArray : any = [{"id":"1","summary":"These are the results for the searched text","link":"http://www.example.com"}]

This resultArray is fetched from hitting the backend service by sending the search text as input. Based on the search text, the result is fetched. Need to highlight the searched text, similar to google search. Please find the screenshot,

enter image description here

If I search for the word "member", the occurence of the word "member" gets highlighted. How to achieve the same using angular 2. Please suggest an idea on this.

angular typescript html javascript
7 Answers

If you have multiple words in your string than use pipe which accepts array and highlight each word in result.

You can use following pipe for multiple search words:- 

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
    name: 'highlight'
})

export class HighlightText implements PipeTransform {

    transform(value: any, args: any): any {
        if (!args) {return value;}
        for(const text of args) {
            var reText = new RegExp(text, 'gi');
            value = value.replace(reText, "<mark>" + text + "</mark>");
            //for your custom css
            // value = value.replace(reText, "<span class='highlight-search-text'>" + text + "</span>"); 


        }
        return value;
    }
}

Split you string to generate array of strings.

var searchTerms = searchKey.split(' ');

usage:

<div [innerHTML]="result | highlight:searchTerms"></div>

If you wanted to use custom class :

.highlight-search-text {
  color: black;
  font-weight: 600;
}

All the best!

user_112537120

Building on a previous answer (HighlightedText-Component) I ended up with this:

import { Component, Input, OnChanges } from "@angular/core";

@Component({
    selector: 'highlighted-text',
    template: `
        <ng-container *ngFor="let match of result">
            <mark *ngIf="(match === needle); else nomatch">{{match}}</mark>
            <ng-template #nomatch>{{match}}</ng-template>
        </ng-container>
    `,
})
export class HighlightedTextComponent implements OnChanges {
    @Input() needle: string;
    @Input() haystack: string;
    public result: string[];

    ngOnChanges() {
        const regEx = new RegExp('(' + this.needle + ')', 'i');
        this.result = this.haystack.split(regEx);
    }
}

This way also multiple matches of the needle are highlighted. The usage of this component is similar to the one in the previous answer:

<highlighted-text [needle]="searchInput" [haystack]="value"></highlighted-text>

For me this approach using a component feels more secure, since I do not have to use "innerHtml".

user_27676260

I would suggest to escape the search String like this

 RegExp.escape = function(string) {
  if(string !== null){ return string.toString().replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
  } else return null
};

@Pipe({
    name: 'highlight'
})
export class HighlightPipe implements PipeTransform {
  constructor(private sanitizer: DomSanitizer){ }

  transform(value: any, args: any): any {
    if (!args || value == null) {
      return value;
    }
    // Match in a case insensitive maneer
    const re = new RegExp(RegExp.escape(args), 'gi');

      const  match = value.match(re);



    // If there's no match, just return the original value.
    if (!match) {
      return value;
    }

    const replacedValue = value.replace(re, "<mark>" + match[0] + "</mark>")
    return this.sanitizer.bypassSecurityTrustHtml(replacedValue)
  }
}
user_123252700
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