Get Total Post Count With found_posts in WP_Query

functions-get_post.php

<?php

$args = array(
	'posts_per_page' => -1,
	'meta_query' => array(
		array(
			'key' => 'foo',
			'value' => 'bar'
		)
	),
	'cache_results' => false,
	'fields' => 'ids'
);
$posts = get_posts( $f_args );
$total_post_count = count( $posts );

functions.php

<?php

$args = array(
	'post_status' => 'publish',
	'meta_query' => array(
		array(
			'key' => 'foo',
			'value' => 'bar'
		)
	)
);
$posts = new WP_Query( $args );
$total_post_count = $posts->found_posts;

scripts.js

//...
//Main controller
app.controller('Main', ['$scope', '$http', function($scope, $http) {
	$http.get('wp-json/taxonomies/category/terms').success(function(res){
		$scope.categories = res;
	});

	$http.get('wp-json/posts/').success(function(res, status, headers){
		$scope.posts = res;
		$scope.pageTitle = 'Latest Posts:';
		document.querySelector('title').innerHTML = 'Home | AngularJS Demo Theme';

		console.log(headers('X-WP-Total'));
	});
}]);
//...

Snippets from my post Counting Posts In WordPress.