请问为什么javascript中的prompt（）没执行location.href就跳转了

Question

我的函数内容写的是：
var emailinput = prompt("Input your Email", "");
location.href = 'test.php?e=' + jemailinput;

Answer 1

var emailinput = prompt("Input your Email", "");if(emailinput != '' && emailinput != null) location.href = 'test.php?e=' + emailinput;

Answer 2

var emailinput = prompt("Input your Email", "");if(emailinput)location.href = 'test.php?e=' + jemailinput;