如何使函数接受参数作为JavaScript中的字符串

Question

Think this is a simple question but just can' get my head around it;

So have these:

var students = ["Joseph", "Susan", "William", "Elizabeth"]

var scores = [ [80, 70, 70, 100], [85, 80, 90, 90], [75, 70, 80, 75], [100, 90, 95, 85] ]

var gradebook = {
Joseph: {
   testScores: scores[0]
},
Susan: {
    testScores: scores[1]
 },
William: {
   testScores: scores[2]
},
Elizabeth: {
   testScores: scores[3]
},
addScore: function(name, score) {
    gradebook[name]["testScores"].push(score);
 },
getAverage: function(name) {
    average(gradebook[name]["testScores"]);
  }
};

var average = function(array) {
  return array.reduce(function(a, b) { return a + b }) / array.length;
};

Have 2 arrays, and gradebook object, want to call gradebook.getAverage("Joseph") and return the average. but this line average(gradebook[name]["testScores"]); in getAverage function I don't think is working.

When I put the code into node terminal and then do gradebook.getAverage("Joseph"); i get undefined.

If I do average(gradebook["Joseph"]["testScores"] in the terminal I get the answer I want.

Hopefully this makes sense! thanks

Answer 1

The reason you are getting undefined from the function call is that they are not returning any value. Change it to this:

addScore: function(name, score) {
    return gradebook[name]["testScores"].push(score);
 },
getAverage: function(name) {
    return average(gradebook[name]["testScores"]);
  }
};

Answer 2

You need to return the value from the getAverage method:

getAverage: function(name) {
  return average(gradebook[name]["testScores"]);
}