Javascript SyntaxError：缺少； before语句（for循环之后）

Question

I keep getting this error and it's confusing me..

function calculate(){
    var n = document.getElementById("noOfCourses").value;
    for(var i = 0 ; i < n ; i++) {
        var course[i] = document.getElementById("GPA" + i+1).value;
        var hours[i] = document.getElementById("hours" + i+1).value;
        // Calculate the product of Course GPA and Credit Hours
        var product[i] = course[i] * hours[i];
    }
}

Answer 1

Basically you need to declare and initialise arrays before using them.

function calculate(){
    var n = document.getElementById("noOfCourses").value,
        course = [],  // declare and init before
        hours = [],   // declare and init before
        product = []; // declare and init before

    for(var i = 0 ; i < n ; i++) {
        course[i] = document.getElementById("GPA" + i+1).value;
        hours[i] = document.getElementById("hours" + i+1).value;
        // Calculate the product of Course GPA and Credit Hours
        product[i] = course[i] * hours[i];
    }
}

Answer 2

The var keyword is used to declare new variables, and optionally initialize them. It's not used in ordinary assignments. And it makes no sense to include an index in the variable being declared -- indexes are used to access the contents of an array, not declare anything.

function calculate(){
    var n = document.getElementById("noOfCourses").value;
    for(var i = 0 ; i < n ; i++) {
        course[i] = document.getElementById("GPA" + i+1).value;
        hours[i] = document.getElementById("hours" + i+1).value;
        // Calculate the product of Course GPA and Credit Hours
        product[i] = course[i] * hours[i];
    }
}