驗證後的Javascript填充表格

Question

我正在爲我的JavaScript類做一個表單，並且我被卡住了它的某個部分。我有一個單獨的驗證器JavaScript文件，並調用該HTML文件的功能。所有的驗證工作，如果表單區域未填寫。我想要做的是，如果字段留空，他們將無法驗證，並將值插入該字段。下面是表單字段的示例，html頁面中的javascript函數以及外部驗證器js文件。在HTML頭

通話功能：

function formvalidation(thisform) { 
with (thisform) { 
if (textbox_validation(first_name,"Please enter your first name.")==false) 
{first_name.blur(); return false;}; 
if (textbox_validation(business_name,"Please enter your business. Please enter N/A if 
you do not have one.")==false) { business_name.focus(); return false; 
business_name.value=="N/A";}; 

外部JS驗證：

function textbox_validation(entered, alertbox) { 
with (entered) { 
if (value==null || value=="") { 
    alert(alertbox); 
    return false; 
} 
else { 
    return true; 
    } 
    } 
} 

因此驗證工作，重點是空字段，但是對於我的一些領域我他們想如果驗證失敗或者如果它沒有填充int，則填充一定的值。 business_name行代碼是當我試圖使其工作。任何幫助深表感謝！

Answer 1

Ordinarilly，你不會使用警報，而是會放的錯誤信息，span或div要麼靠近input或在form的頂部（或底部）。另外（如@Frits van Campen提到的）它是generally bad practice to use with 嘗試這樣代替：

function textbox_validation(entered, errormsg) { 
    var errbox = document.getElementById(entered.id + '-errors'); // just to prevent writing it twice 
    // Note this requires the input to have an id, and the errer box's id to be the same with an '-errors' suffix. 

    // Instead of using with, just acces properties normally 
    if (!entered.value) { // The `!` "neggation" operater makes "falsy" values `true` 
         // "falsy" values include `false`, the empty string, `0`, `null`, `undefined`, `NaN` and a few others 
     // Put the error message in the DOM instead of alerting it 
     errbox.innerHTML = errormsg; 
     return false; 
    } 
    else { 
     // Wipe any previous error messages 
     errbox.innerHTML = ''; 
     return true; 
    } 
} 

而對於形式驗證，再一次;我們不要使用with。而且，試圖assing「N/A」的值時，你使用的比較運營商，而不是分配運營商，並且你做到了返回後：

function formvalidation(thisform) { 
    // just use the `!` "negation" operator 
    if (!textbox_validation(thisform.first_name, 
     "Please enter your first name.")) 
    { 
     thisform.first_name.blur(); 
     return false; 
    } 
    if (!textbox_validation(business_name, 
     "Please enter your business. Please enter N/A if you do not have one.")) 
    { 
     thisform.business_name.focus(); 
     thisform.business_name.value = "N/A"; // for assignment, use `=`. `==` and `===` are used for comparison 
     return false; // a return statement ends the function, make sure it's after anything you want to execute! 
    } 
} 

Answer 2

使用DOM設置字段的佔位符。喜歡這個。

var myInput = document.getElementById('input1'); 
myInput.placeholder = 'This validation has failed.';