javascript：警报在任何浏览器中均不起作用，为什么

Question

i have simple javascript code but the alert does not work in any browser my code is:

 function ChangeText(){
    document.getElementById("p1").innerHTML = "dorood";
    }
    var students = [student1, student2, student3];
    var student1 ={FirstName:"saeed",LastNmae:"alavi",Age:"1992"};
    var student2 = { FirstName: "mohammad", LastNmae: "alavi", Age: "1992" };
    var student3 = { FirstName: "hosein", LastNmae: "alavi", Age: "1992" };
    alert(students[1].FirstName);

Answer 1

You just needed to move var students = [student1, student2, student3]; the variables you were referring to, weren't assigned.

  var student1 ={FirstName:"saeed",LastNmae:"alavi",Age:"1992"}; var student2 = { FirstName: "mohammad", LastNmae: "alavi", Age: "1992" }; var student3 = { FirstName: "hosein", LastNmae: "alavi", Age: "1992" }; var students = [student1, student2, student3]; alert(students[1].FirstName); 

Answer 2

You can create the array only after individual objects are created.

 function ChangeText() { document.getElementById("p1").innerHTML = "dorood"; } var student1 = { FirstName: "saeed", LastNmae: "alavi", Age: "1992" }; var student2 = { FirstName: "mohammad", LastNmae: "alavi", Age: "1992" }; var student3 = { FirstName: "hosein", LastNmae: "alavi", Age: "1992" }; var students = [student1, student2, student3]; alert(students[1].FirstName); 

Answer 3

You must be getting following error which is clear

"Uncaught TypeError: Cannot read property 'FirstName' of undefined"

Define variables student1,student2... before using them when initializing students array.

 function ChangeText() { document.getElementById("p1").innerHTML = "dorood"; } var student1 = { FirstName: "saeed", LastNmae: "alavi", Age: "1992" }; var student2 = { FirstName: "mohammad", LastNmae: "alavi", Age: "1992" }; var student3 = { FirstName: "hosein", LastNmae: "alavi", Age: "1992" }; var students = [student1, student2, student3]; console.log(students[1].FirstName);