# Highlight Transform service

Adds HTML to a string to highlight chosen sections.

## Methods

`public highlight(text: string, search: string, wrapperClass: string = 'highlight'): HightlightTransformResult`<br/>
Searches for `search` string(s) within `text` and highlights all occurrences.

## 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 &lt;span&gt; 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 &lt;span&gt; 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.

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## See also

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