Get random word and its parameters from json file

I am trying to get the random word and its parameter from the JSON file.

JSON file:

{
    ranWord1 {
        sentence: "This is a sentence 1"
    },
    ranWord2 {
        sentence: "This is a sentence 2"
    },
    ranWord3 {
        sentence: "This is a sentence 3"
    },
    ranWord4 {
        sentence: "This is a sentence 4"
    },
    ranWord5 {
        sentence: "This is a sentence 5"
    }
}

JS:

function readFiles() {
    var result = null;
    var file = 'dictionary.json';
    $.ajax({
        url: file,
        type: 'get',
        dataType: 'json',
        async: false,
        success: function(data) {
            result = data;
        } 
    });
    var lines = result.split(", ");
    var randLineNum = Math.floor(Math.random() * lines.length);
    return lines[randLineNum];
}

I am able to get the random word which in this case is ranWord1, ranWord2, ranWord3, ranWord4, ranWord5. But, I am not able to get the parameters. I would like to store, for example, "This is a sentence 4" in a local variable. Any help will be appreciated!

UPDATE:

External word.js file:

var data = [
  ["ranWord1", "This is a sentence 1"],
  ["ranWord2", "This is a sentence 2"],
  ["ranWord3", "This is a sentence 3"],
  ["ranWord4", "This is a sentence 4"],
  ["ranWord5", "This is a sentence 5"]
]

JS:

function readFiles() {
var result = null;
        var file = 'word.js';
        $.ajax({
            url: file,
            type: 'get',
            data: 'data',
            dataType: 'script',
            async: false,
            success: function(data) {
                var randomData = data[Math.floor(Math.random() * data.length)];
                result = randomData;
                alert("word: " + randomData[0] + ", sentence: " + randomData[1]);
            }
        });
}

I am trying to get the array from an external file but now I am getting undefined for randomData[1] and I am getting anything including [ and ] for word