CoreJS: Functions

Fun with Functions

1. Write a function which receives a number parameter and returns the square of that number.

2. Write a function which receives one parameter, an array of numbers, and returns the mean of those numbers. (Hint: you'll need a loop.)

3. Write a function which receives an integer up to 10 and returns the corresponding word (i.e. 'one', 'two', 'three', etc). (Hint: you'll need an array.)

4. Use your three functions together to print the word for the square of the mean of these numbers: [2,4,7,-1]

More fun: emulating array functions

1. Write a function called myPush which receives an array and a value, and then behaves just like ordinary push: it should append the value to the array and return its new length. Avoid using the built-in push method in your implementation.

2. Write a function called muyPush which receives two arrays, pushes all the elements of the second array onto the end of the first, and returns the new length of the first.

3. Write a function called myConcat which receives two arrays and returns a new array comprising a copy of the first with a copy of the second appended to the end. Neither of the input arrays should change. Avoid using built-in concat in your implementation.

assert

Write a function called assert which will receive parameters claim and warning. claim is the result of a Boolean expression, and if claim is not truthy, assert should console.log the string stored in parameter warning.

Scope and Shadowing

Predict what will happen in each of the following programs:

1.

    var x=1, y=1;
    function fun() {
        x=3;
        console.log('x='+x, 'y='+y);
    }
    fun();
    console.log('x='+x, 'y='+y);

2.

    var x=1, y=1;
    function fun(x) {
        x=3;
        console.log('x='+x, 'y='+y);
    }
    fun(2);
    console.log('x='+x, 'y='+y);

3.

    var x=1, y=1;
    function fun(z) {
        x=3;
        console.log('x='+x, 'y='+y);
    }
    fun(2);
    console.log('x='+x, 'y='+y);

4.

    var x=1, y=1;
    function fun(x) {
        x=3, y=3;
        if (x) {
            var y=4;
            console.log('x='+x, 'y='+y);
        }
        console.log('x='+x, 'y='+y);
    }
    fun(2);
    console.log('x='+x, 'y='+y);

5.

    var x=1, y=1;
    function showXY(x,y) {
        console.log('x='+x, 'y='+y);
    }
    function fun(x) {
        x=3;
        showXY(x,y);
    }
    fun(2);
    showXY(x,y);

6.

    var x=1, y=1;
    function showXY() {
        console.log('x='+x, 'y='+y);
    }
    function fun(x) {
        x=3;
        showXY();
    }
    fun(2);
    showXY();

7.

    var x=1, y=1;
    function fun(x) {
        function showXY() {
            console.log('x='+x, 'y='+y);
        }
        x=3;
        showXY();
    }
    fun(2);
    showXY();

Samples

scratchpad