How to Fix JavaScript HTML Element Did Not Show an Error?

TypeScript code is as follows:

namespacesLab.ts:

var ArrayUtilities;
(function (ArrayUtilities) {
    function reverseArray(array) {
        return array.slice(0).reverse();
    }
    ArrayUtilities.reverseArray = reverseArray;
    function lastItemOfArray(array) {
        return array.slice(0).pop();
    }
    ArrayUtilities.lastItemOfArray = lastItemOfArray;
    function firstItemOfArray(array) {
        return array.slice(0).shift();
    }
    ArrayUtilities.firstItemOfArray = firstItemOfArray;
    function concatenateArray(array1, array2) {
        return array1.concat(array2);
    }
    ArrayUtilities.concatenateArray = concatenateArray;
})(ArrayUtilities || (ArrayUtilities = {}));

HTML code is as follows:

index.html:

When I click the index.html, a webpage showing four buttons appears. However, there is no array displayed.

expected result: four buttons and an array shown on the webpage

actual result: the array did not show on the webpage

Answer

you have a space in your ID:

change

to