Maths using randomly selected symbols

JavaScript
1

I am randomly selecting the maths symbol (+,-,*,/) using a math.random and then applying the relevant symbol to a variable based on the result, ie if result == 1 then symbolGen = “+”

I now need to use this symbol in the Javascript for it’s original purpose, as I have two other numbers being generated and need to work out the answer.

Many thanks in advance,

Chris

2

What code do you have so far?

3

Let’s go crazy and use functions to perform the operations.

This is not how you would do it for a class where you’re supposed to lean about other things, but it could be instructive in other ways.


var add = function (a, b) {
    return a + b;
},
    subtract = function (a, b) {
    return a - b;
},
    multiply = function (a, b) {
    return a * b;
},
    divide = function (a, b) {
    return a / b;
},
    operations = [
    {symbol: '+', fn: add},
    {symbol: '-', fn: subtract},
    {symbol: '*', fn: multiply},
    {symbol: '/', fn: divide}
],
    i,
    type,
    operation,
    a,
    b,
    result = '';
for (i = 0; i < 10; i += 1) {
    type = Math.floor(Math.random() * operations.length, 10);
    operation = operations[type];
    a = Math.floor(Math.random() * 10);
    b = Math.floor(Math.random() * 10);
    result += a + ' ' + operation.symbol + ' ' + b + ' = ' + operation.fn(a, b) + '\
';
}
window.alert(result);
4

Firstly, thank you for the swift replies. Secondly, unfortunately I am not overly confident in Javascript so I am somewhat overwhelmed by your reply pmw57. The code I have so far is…


var firstNo = Math.floor(Math.random() * 12+1);
            var secondNo = Math.floor(Math.random() * 12 + 1);
            var mathsSymbol = "";
            var symbolGen = Math.floor(Math.random() * 4 + 1);
            var completeEquation;
            var answer;

            if (symbolGen == 1) {
                mathsSymbol = "+";
            } else if (symbolGen == 2) {
                mathsSymbol = "-";
            } else if (symbolGen == 3) {
                mathsSymbol = "*";
            } else {
                mathsSymbol = "/";
            }

            answer = firstNo + mathsSymbol.hasOwnProperty + secondNo;

            completeEquation = firstNo + " " + mathsSymbol + " " + secondNo + " =  " + answer;

            var question = document.getElementById('equation');
            question.innerHTML = completeEquation;

Do you think you could possibly explain a method of modifying the code to incorporate your answer. It was very good but I need some help understanding it.

Many thanks,

Chris

5

There is only one way to move on from where you are, and that is to use the eval method to evaluate the result of a string.

However, eval is considered evil so it is better to use other techniques.

For example, this would work with your existing code:


if (symbolGen == 1) {
    answer = firstNo + secondNo;
} else if (symbolGen == 2) {
    answer = firstNo - secondNo;
} else if (symbolGen == 3) {
    answer = firstNo * secondNo;
} else {
    answer = firstNo / secondNo;
}