1

Here is my javascript program and it supposed to output the alert statement at the bottom of the code but is not apppearing. Why is it?

//function mean
function mean(values, callback) {
    var total = 0;
    for (var i = 0, max = values.length; i < max; i++) {
        if (typeof callback === "function") {
            total += callback(value[i]);
        } else {
            total += values[i];
        }
    }
}

var result = mean([2, 5, 7, 11, 4], function (x) {
    return 2 * x;
});

alert("The result mean is " + result + ".");
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6
  • 4
    total += callback(value[i]); -- should be values not value. Keep your browser console open so that you can see errors reported. Commented Mar 15, 2016 at 16:40
  • Value is not defined Commented Mar 15, 2016 at 16:42
  • check your console for errors in JavaScript Commented Mar 15, 2016 at 16:43
  • You have to write values[i] and return the variable total in order to get a result other than undefined., Commented Mar 15, 2016 at 16:43
  • 2
    You can answer that question yourself if you learn how to debug JavaScript. Stack Overflow is not a debugging service. Commented Mar 15, 2016 at 16:46

3 Answers 3

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3

You need to return total and change valueto values.

function mean(values, callback) {
    var total = 0;
    for (var i = 0, max = values.length; i < max; i++) {
        if (typeof callback === "function") {
            total += callback(values[i]);
        } else {
            total += values[i];
        }
    }
    return total;
}

var result = mean([2, 5, 7, 11, 4], function (x) {
    return 2 * x;
});

alert("The result mean is " + result + ".");

You can rewrite the code to a more compact way:

function mean(values, callback) {
    callback = callback || function (x) { return x; };
    return values.reduce(function (r, a) {
        return r + callback(a);
    }, 0);
}

var result = mean([2, 5, 7, 11, 4], function (x) {
    return 2 * x;
});

alert("The result mean is " + result + ".");

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Comments

2

Along with the typo mentioned by Pointy, If I am reading it right, you never return a value from mean, try returning total

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0

You have to return total in your callback function and make sure values variables are not typed as value.

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