Edit in JSFiddle

// Mock.mock(rurl, function(options))
Mock.mock(/\.json/, function(options) {
    return options
})
$.ajax({
    url: 'hello.json',
    dataType: 'json'
}).done(function (data, status, jqXHR) {
    $('<pre>').text(JSON.stringify(data, null, 4))
        .appendTo('body')
})

<!-- （必选）加载 Mock -->
<script src="http://mockjs.com/dist/mock.js"></script>