一段javascript代碼的解釋

Question

我是一名JavaScript初學者，我正在看下面這段代碼。

var type_select = '<select id="type_select" style="margin-bottom:0px;">'; 
    var i; 
    var customer_group = <?php echo json_encode($customer_group);?>; 
    for (i = 0; i < customer_group.length; ++i) { 
     //console.log(customer_group[i].group_id); 
     if (customer_group[i].group_name == table_column_1){ 
      type_select = type_select+'<option value='+customer_group[i].group_id+' selected>'+customer_group[i].group_name+'</option>'; 
     }else{ 
      type_select = type_select+'<option value='+customer_group[i].group_id+'>'+customer_group[i].group_name+'</option>'; 
     } 
    } 
    type_select = type_select+'</select>'; 
    //not allow to click header 
    if (col == 0) { 
     return; 
    } 

請幫助給我一些它可能在做什麼的想法。也許有些方向。我不確定這段代碼是否足夠，請儘量幫助我，並儘可能地向我解釋。您的幫助將非常感謝。

Answer 1

它建立一個選擇下拉框中的一些選項

<select id="type_select" style="margin-bottom:0px;"> 
    <option value="some-value">Some text</option> 
    <option value="some-other-value">Some other text</option> 
    <option value="yet-another-value" selected>More text this one is selected on load</option> 
</select> 

綜觀您發佈的代碼片斷，然後它確實有它

希望絕對沒有任何幫助

Answer 2

var type_select = '<select id="type_select" style="margin-bottom:0px;">'; 
var i; 

// this part of code will be interpreted by PHP Engine, on client side you will find an JSON representation of 
// "Customer_group", probably gotten from database, or file 
var customer_group = <?php echo json_encode($customer_group);?>; 

for (i = 0; i < customer_group.length; ++i) { 
    // here, you are building a HTML string, this will be attached to DOM using 
    // ex : document.getElementById('YOUR_DOM_ID').innerHTML = type_select; 
    if (customer_group[i].group_name == table_column_1){ 
     type_select = type_select+'<option value='+customer_group[i].group_id+' selected>'+customer_group[i].group_name+'</option>'; 
    }else{ 
     type_select = type_select+'<option value='+customer_group[i].group_id+'>'+customer_group[i].group_name+'</option>'; 
    } 
} 
type_select = type_select+'</select>'; 
//not allow to click header 
if (col == 0) { 
    return; 
}