$interpolate

Compiles a string with markup into an interpolation function. This service is used by the HTML $compile service for data binding. See $interpolateProvider for configuring the interpolation markup.

var $interpolate = ...; // injected
var exp = $interpolate('Hello {{name | uppercase}}!');
expect(exp({name:'Angular'})).toEqual('Hello ANGULAR!');

$interpolate takes an optional fourth argument, allOrNothing. If allOrNothing is true, the interpolation function will return undefined unless all embedded expressions evaluate to a value other than undefined.

var $interpolate = ...; // injected
var context = {greeting: 'Hello', name: undefined };

// default "forgiving" mode
var exp = $interpolate('{{greeting}} {{name}}!');
expect(exp(context)).toEqual('Hello !');

// "allOrNothing" mode
exp = $interpolate('{{greeting}} {{name}}!', false, null, true);
expect(exp(context)).toBeUndefined();
context.name = 'Angular';
expect(exp(context)).toEqual('Hello Angular!');

allOrNothing is useful for interpolating URLs. ngSrc and ngSrcset use this behavior.

####Escaped Interpolation $interpolate provides a mechanism for escaping interpolation markers. Start and end markers can be escaped by preceding each of their characters with a REVERSE SOLIDUS U+005C (backslash). It will be rendered as a regular start/end marker, and will not be interpreted as an expression or binding.

This enables web-servers to prevent script injection attacks and defacing attacks, to some degree, while also enabling code examples to work without relying on the ngNonBindable directive.

For security purposes, it is strongly encouraged that web servers escape user-supplied data, replacing angle brackets (<, >) with &lt; and &gt; respectively, and replacing all interpolation start/end markers with their escaped counterparts.

Escaped interpolation markers are only replaced with the actual interpolation markers in rendered output when the $interpolate service processes the text. So, for HTML elements interpolated by $compile, or otherwise interpolated with the mustHaveExpression parameter set to true, the interpolated text must contain an unescaped interpolation expression. As such, this is typically useful only when user-data is used in rendering a template from the server, or when otherwise untrusted data is used by a directive.

<div ng-init="username='A user'">
  <p ng-init="apptitle='Escaping demo'">{{apptitle}}: \{\{ username = "defaced value"; \}\}
    </p>
  <p><strong>{{username}}</strong> attempts to inject code which will deface the
    application, but fails to accomplish their task, because the server has correctly
    escaped the interpolation start/end markers with REVERSE SOLIDUS U+005C (backslash)
    characters.</p>
  <p>Instead, the result of the attempted script injection is visible, and can be removed
    from the database by an administrator.</p>
</div>