Javascript with callback function not working

user6035846 Published at Dev

user6035846

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 + ".");

Nina Scholz

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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