javascript - 字符方法 javascript

Question

有问题......谁能告诉我我在这段 JavaScript 代码上做错了什么：

function getname() {
    var the_name = window.prompt("Enter your first name", "");
    var first_char = the_name.charAt(0);

    if(first_char = "S") then {
        document.write(the_name);
    } else {
        window.alert("Please enter a name that starts with an uppercase S to have it displayed.");
    }
}

Answer 1

then语法无效，在字符串比较时 使用==

function getname() 
{
var the_name=window.prompt("Enter your first name","");
var first_char = the_name.charAt(0);

if(first_char== "S") 
{
    document.write(the_name);
}
else
{
    window.alert("Please enter a name that starts with an uppercase S to have it displayed.");
}
}

Answer 2

尝试改变

if(first_char= "S")

至

if(first_char== "S")

JavaScript 比较和逻辑运算符

Answer 3

尝试使用==来比较您的价值，而不是=：

if(first_char == "S") 

以及删除then您的 if-else 条件（实际上我认为这是您的解释：P）

Answer 4

语法中没有then 。if-else比较运算符==也不是=

function getname() 
{
var the_name=window.prompt("Enter your first name","");
var first_char = the_name.charAt(0);

if(first_char== "S") 
{
    document.write(the_name);
}
else
{
    window.alert("Please enter a name that starts with an uppercase S to have it displayed.");
}
}