---
Added: v2.0.0
Status: Active
---
# Highlight Transform service

Adds HTML to a string to highlight chosen sections.

## Methods

-   `highlight(text: string, search: string, wrapperClass: string = 'highlight'): HightlightTransformResult`  
    Searches for `search` string(s) within `text` and highlights all occurrences.  
    -   `text` - Text to search within
    -   `search` - Text pattern to search for
    -   `wrapperClass` - CSS class used to provide highlighting style

## Details

A typical use case for this service is to display the results from a search engine.
An excerpt of a retrieved document can be shown with the matching search terms
highlighted to indicate where they were found.

The service works by adding HTML <span> elements around all sections of text
that match the `search` string. You can specify multiple search strings at once by
separating them with spaces, so passing "Apple Banana Cherry" in `search` will
highlight any of those words individually. The <span> element includes a
`class` attribute which defaults to "highlight" but you can pass any class name
you like using the `wrapperClass` parameter.

The resulting text with HTML highlighting is returned within a `HightlightTransformResult`
object:

```ts
interface HightlightTransformResult {
    text: string;
    changed: boolean;
}
```

The `changed` flag will be false if the search string was not found (ie, no highlighting
took place) and true otherwise.

## See also

-   [Text highlight pipe](text-highlight.pipe.md)
-   [Highlight directive](highlight.directive.md)