Uncaught TypeError：無法讀取未定義的屬性'which'。當我使用密鑰時，我遇到同樣的問題

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我試圖按某個鍵時訪問數組中的某個元素。我可以根據w3使用event.which或event.key，但我必須調整x與之相比較的內容。但不管我仍然得到同樣遺漏的類型錯誤：無法讀取屬性「的」未定義或遺漏的類型錯誤的：無法讀取的不確定Uncaught TypeError：無法讀取未定義的屬性'which'。當我使用密鑰時，我遇到同樣的問題

var i = 0; // Start point 
var pages_arr = []; // Pages array 

pages_arr[0] = "JS_CSS_HTML_HW_home_page.html"; 
pages_arr[1] = "JS_CSS_HTML_HW_courses_page.html"; 
pages_arr[2] = "JS_CSS_HTML_HW_projects_page.html"; 
pages_arr[3] = "JS_CSS_HTML_HW_hobbies_page.html"; 
pages_arr[4] = "JS_CSS_HTML_HW_friends_page.html"; 

function keyTabChange(event){ 

var x = event.which; 
// Unicode for Up = 38 
// Unicode for Right = 39 
// Unicode for left = 37 
// Uniceode for downn = 40 
//var curr_window = window.location.href; // Get URL of string of webpage location 

//i = pages_arr.indexOf(curr_window); // Get the index of that location in the array of pages 

if (x == 38 || x == 37){ // Previous tab 
    if (i == 0){ 
     i = pages_arr.length - 1; // If index at first element in array go to end of the array 
    } 
    else{ 
     --i; // All other cases go to previous tab 
    }  

} 
else if (x== 39 || x == 40){ // Next tab 
    if (i==pages_arr.length - 1){ 
     i = 0; // If index is at last element go to first element of array 

    } 
    else{ 
     ++i; // All other cases go to next tab 
    } 

} 
//window.location.assign(pages_arr[i]); // Load page of the URL 
//document.write(pages_arr[i]); 

document.getElementById("TestID").innerHTML = pages_arr[i];

財產「鍵」}

document.addEventListener（「KEYUP」 keyTabChange（事件））; 強文本

來源

2017-10-17 Daniel Erhabor

'document.addEventListener（「KEYUP」，keyTabChange（事件））;'=>'document.addEventListener（「KEYUP」，keyTabChange）;'，看到鏈接的問題對爲什麼的答案。 –